U.S. patent number 7,599,060 [Application Number 12/222,820] was granted by the patent office on 2009-10-06 for optical scanning configurations, systems, and methods involving at least one actuator for scanning a scan head.
This patent grant is currently assigned to Applied Biosystems, LLC. Invention is credited to Steven J. Boege, Jon A. Hoshizaki, Howard G. King, Mark F. Oldham, Johannes P. Sluis.
United States Patent |
7,599,060 |
Hoshizaki , et al. |
October 6, 2009 |
Optical scanning configurations, systems, and methods involving at
least one actuator for scanning a scan head
Abstract
An optical system includes a sample substrate having a surface,
the surface defining a 2-dimensional sample plane. The system
includes an excitation source configured to provide excitation
light to the sample substrate. The system further includes an
optical detector configured to receive emission light from the
sample substrate and generate detection data. The system also
includes a scan head configured at least (i) to direct the
excitation light towards the sample substrate, (ii) to receive
emission light from the sample substrate and direct the emission
light towards the optical detector, and (iii) for scanning relative
to the sample substrate. The system includes at least one actuator
configured to scan the scan head relative to the sample substrate,
the at least one actuator being configured to provide at least one
of (1) a relative linear motion and a relative angular motion about
a rotational axis generally perpendicular to the sample plane and
(2) two relative angular motions about two respectively different
rotational axes generally perpendicular to the sample plane.
Inventors: |
Hoshizaki; Jon A. (Cupertino,
CA), King; Howard G. (Berkeley, CA), Sluis; Johannes
P. (Redwood City, CA), Boege; Steven J. (San Mateo,
CA), Oldham; Mark F. (Los Gatos, CA) |
Assignee: |
Applied Biosystems, LLC
(Carlsbad, CA)
|
Family
ID: |
46323092 |
Appl.
No.: |
12/222,820 |
Filed: |
August 18, 2008 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20080316482 A1 |
Dec 25, 2008 |
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Related U.S. Patent Documents
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Application
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Filing Date |
Patent Number |
Issue Date |
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11265110 |
Nov 3, 2005 |
7423750 |
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10981440 |
Nov 4, 2004 |
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10440719 |
May 19, 2003 |
7387891 |
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10216620 |
Aug 9, 2002 |
7008789 |
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09700536 |
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6818437 |
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PCT/US99/11088 |
May 17, 1999 |
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Current U.S.
Class: |
356/317; 436/172;
435/288.7; 422/82.08; 250/458.1 |
Current CPC
Class: |
G05D
23/20 (20130101); G05D 23/1919 (20130101); G01N
21/6452 (20130101); F21V 29/54 (20150115); G01N
21/645 (20130101); F21V 29/763 (20150115); F21V
29/677 (20150115); G01N 2201/062 (20130101); G01N
2021/6439 (20130101); G01N 2201/1211 (20130101) |
Current International
Class: |
G01N
21/64 (20060101) |
Field of
Search: |
;356/317,318,417
;250/458.1,459.1,461.1,461.2 |
References Cited
[Referenced By]
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Primary Examiner: Evans; F. L
Attorney, Agent or Firm: Feldstein; Mark
Parent Case Text
I. CROSS-REFERENCES TO RELATED APPLICATIONS
The present application is a continuation of co-pending application
Ser. No. 11/265,110, filed on Nov. 3, 2005, which is a
continuation-in-part of co-pending U.S. patent application Ser. No.
10/981,440 filed on Nov. 4, 2004, which in turn is a
continuation-in-part of co-pending U.S. patent application Ser. No.
10/440,719, filed May 19, 2003, which in turn is a
continuation-in-part of co-pending U.S. patent application Ser. No.
10/216,620, filed Aug. 9, 2002, which in turn is a continuation of
co-pending U.S. patent application Ser. No. 09/700,536, filed Nov.
29, 2001, which claims priority to PCT/US99/11088, filed May 17,
1999, which published as publication number WO 99/60381 on Nov. 25,
1999, all of which are incorporated herein in their entireties by
reference.
Cross-reference is made to co-pending U.S. patent application Ser.
No. 10/440,920 entitled "Optical Instrument Including Excitation
Source" to Boege et al., co-pending U.S. patent application Ser.
No. 10/440,852 entitled "Apparatus And Method For Differentiating
Multiple Fluorescence Signals By Excitation Wavelength" to King et
al., both filed on May 19, 2003, and U.S. patent application Ser.
No. 10/735,339, filed Dec. 12, 2003, Reexamination Control No.
90/007,275, filed, Oct. 29, 2004, for U.S. Pat. No. 6,211,989,
including U.S. Pat. No. 6,211,989, all of which are incorporated
herein in their entireties by reference.
Claims
What is claimed is:
1. An optical system, comprising: a) a sample substrate having a
surface, the surface defining a 2-dimensional sample plane; b) an
excitation source configured to provide excitation light to the
sample substrate; c) an optical detector configured to receive
emission light from the sample substrate and generate detection
data; d) a scan head configured at least (i) to direct the
excitation light towards the sample substrate, (ii) to receive
emission light from the sample substrate and direct the emission
light towards the optical detector, and (iii) for scanning relative
to the sample substrate; and e) at least one actuator configured to
scan the scan head relative to the sample substrate, the at least
one actuator being configured to provide at least one of (1) a
relative linear motion and a relative angular motion about a
rotational axis generally perpendicular to the sample plane and (2)
two relative angular motions about two respectively different
rotational axes generally perpendicular to the sample plane.
2. An optical system according to claim 1, wherein the system is
configured for rectilinear scanning of the scan head relative to
the sample substrate surface.
3. An optical system according to claim 1, wherein the system is
configured for point-by-point scanning of the scan head relative to
the sample substrate surface.
4. An optical system according to claim 1, wherein the optical
detector comprises first and second optical detectors configured to
receive the emission light from the sample substrate and generate
the detection data wherein the first optical detector is configured
to receive a first optically distinct range of the emission light
and the second optical detector is configured to receive a second
optically distinct range of the emission light.
5. An optical system according to claim 1, wherein the excitation
source comprises the first and second LEDs, the first and second
LEDs being configured to provide respectively optically distinct
ranges of excitation light.
6. An optical system according to claim 1, wherein the scanning
comprises the relative linear motion and the relative angular
motion, the at least one actuator comprising a linear actuator
having a linear travel axis aligned generally parallel to the
sample plane and configured to provide linear movement of the scan
head relative to the sample substrate along the linear travel axis;
a rotary actuator having a fixed base and a shaft configured for
rotation about a rotational axis aligned generally perpendicular to
the sample plane, wherein the fixed base is connected to the linear
actuator; and a first arm having a longitudinal axis, a first end,
and a second end, wherein the first end is connected to the
rotational actuator shaft and the second end is connected to the
scan head; the first arm being configured for rotation of its
longitudinal axis generally perpendicularly about the rotational
axis.
7. An optical system according to claim 6, further comprising at
least one bushing aligned parallel to the linear travel axis; and a
platform connected to the linear actuator and configured to travel
along the at least one bushing, wherein the fixed base of the
rotary axis is connected to the platform.
8. An optical system according to claim 1, wherein the scanning
comprises the two relative angular motions, the at least one
actuator comprising a first rotary actuator having a fixed base and
a shaft configured for rotation about a first rotational axis
aligned generally perpendicular to the sample plane; a second
rotary actuator having a fixed base and a shaft configured for
rotation about a second rotational axis aligned generally
perpendicular to the sample plane, wherein the second rotational
axis is aligned generally parallel to the first rotational axis; a
first arm having a longitudinal axis, a first end, and a second
end, wherein the first end is connected to the first rotational
actuator shaft and the second end is connected to the second
rotational actuator fixed base; the first arm being configured for
rotation of its longitudinal axis generally perpendicularly about
the first rotational axis; and a second arm having a longitudinal
axis, a first end, and a second end, wherein the first end is
connected to the second rotational actuator shaft and the second
end is connected to the scan head; the second arm being configured
for rotation of its longitudinal axis generally perpendicularly
about the second rotation axis.
9. An optical system according to claim 1, further comprising at
least one optical fiber having distal and proximal ends, wherein
the at least one optical fiber is configured to conduct the
emission light from its proximal to its distal end; and a fixed
optical head comprising the distal end of the optical fiber and the
optical detector, wherein the fixed optical head is configured to
direct the emission light from the distal end of the optical fiber
towards the optical detector, wherein the scan head is a low mass
scan head comprising the proximal end of the at least one optical
fiber and further configured to direct the emission light to the
distal end of the at least one optical fiber.
10. An optical system according to claim 9, wherein the low mass
scan head further comprises an LED as the excitation source.
11. An optical system according to claim 9, wherein the fixed
optical head comprises the excitation source and is configured to
direct the excitation light into the distal end of the at least one
optical fiber, the optical fiber is configured to direct the
excitation light from its distal to its proximal end, and the low
mass scan head is configured to direct the excitation light from
the proximal end of the optical fiber towards the sample
substrate.
12. An optical system according to claim 9, wherein the fixed
optical head comprises a dispersive spectrometer comprising a
dispersive element and an array detector or multiple optical
detectors configured to measure spectral properties of the
collected emission light.
13. An optical system according to claim 9, comprising an LED as
the excitation source; a thermal control system comprising a
temperature dependent unit comprising at least one of the LED and
the optical detector; and at least one of (1) an active temperature
compensation system comprising a temperature sensor configured to
(i) monitor at least one temperature dependent property of the
temperature dependent unit, and (ii) generate a thermal control
signal related to the at least one temperature dependent property,
and an active temperature compensation system configured to receive
the thermal control signal and regulate at least one of (i) an
operating temperature of the temperature dependent unit and (ii)
the detection data from the optical detector to form temperature
compensated detection data, wherein the regulation is based at
least partially on the thermal control signal, and (2) a passive
temperature compensation system comprising at least one of (i) an
insulating oven at least partially encompassing the temperature
dependent unit, and (ii) a thermally conductive substrate in
thermal contact with the temperature dependent unit and configured
to conduct thermal energy between the temperature dependent unit
and the thermally conductive substrate.
14. An optical system according to claim 9, comprising an LED as
the excitation source; a thermal control system comprising a
temperature dependent unit comprising at least one of the LED and
the optical detector; and an active temperature compensation system
comprising a temperature sensor configured to (i) monitor at least
one temperature dependent property of the temperature dependent
unit, and (ii) generate a thermal control signal related to the at
least one temperature dependent property, and an active temperature
compensation system configured to receive the thermal control
signal and regulate at least one of (i) an operating temperature of
the temperature dependent unit and (ii) the detection data from the
optical detector to form temperature compensated detection data,
wherein the regulation is based at least partially on the thermal
control signal.
15. An optical system according to claim 9, comprising an LED as
the excitation source; a thermal control system comprising a
temperature dependent unit comprising at least one of the LED and
the optical detector; and a passive temperature compensation system
comprising at least one of (i) an insulating oven at least
partially encompassing the temperature dependent unit, and (ii) a
thermally conductive substrate in thermal contact with the
temperature dependent unit and configured to conduct thermal energy
between the temperature dependent unit and the thermally conductive
substrate.
16. An optical system according to claim 13, wherein the at least
one temperature dependent property comprises at least one of a
temperature, a temperature dependent optical property, a
temperature dependent electronic property of the temperature
dependent unit or the temperature sensor, or any combination
thereof.
17. An optical system according to claim 13, wherein the
temperature dependent unit comprises the temperature sensor.
18. An optical system according to claim 13, wherein the
temperature sensor is in thermal contact with the temperature
dependent unit.
19. An optical system according to claim 13, wherein the
temperature sensor is configured to monitor at least one
temperature dependent optical property of the temperature dependent
unit.
20. A method for conducting a scanned optically transduced assay,
comprising a) using an optical system according to claim 1, b)
directing excitation light from the scan bead to the sample
substrate, c) receiving with the optical detector emission light
from the sample substrate, and generating detection data based on
the received emission light, d) scanning the scan head relative to
the sample substrate, the scanning comprising at least one of (1) a
relative linear motion and a relative angular motion about a
rotational axis generally perpendicular to the sample plane and (2)
two relative angular motions about two respectively different
rotational axes generally perpendicular to the sample plane; e)
tracking a position of the scan head relative to the substrate, and
f) correlating the detection data with the position of the scan
head.
21. The optical system of claim 1, wherein the at least one
actuator comprises a plurality of actuators, and the scan head
comprises a plurality of scan heads.
22. The method of claim 20, wherein the at least one actuator
comprises a plurality of actuators, and the scan head comprises a
plurality of scan heads.
Description
II. FIELD
This invention relates to methods and optical systems for optical
scanning of a target sample, including systems having low mass
optical scan heads. The present invention also relates to methods
and systems for performing sample assays, and for producing and
measuring optical responses and signatures.
III. BACKGROUND
A Light-Emitting Diode (LED) can be an excitation source for
optically transduced assays, such as fluorescent measurements. The
need for providing an LED excitation beam source that does not
exhibit excitation beam intensity changes and/or an excitation beam
spectral shift has not been satisfied. A device compatible with
nucleotide amplification reactions, detecting such reactions, and
capable of processing a relatively large number of amplification
reactions is desirable. A device capable of providing enhanced
scanning, such as enhanced scanning speed and enhanced scanning
methods, of multiple reactions or samples is also desirable.
IV. SUMMARY
According to various embodiments, a system and a method configured
to provide optical scanning or interrogation of a sample substrate
is provided where the system is thermally compensated. Thermal
compensation may be, passive, active, or both.
Various embodiments of the invention comprise an optical system and
method having at least one LED configured to provide excitation
light to the sample substrate. The temperature of the LED may, for
example, be thermally stabilized. As another example, detected data
may be adjusted to compensate for temperature-dependent changes in
the LED excitation light, such as changes in its intensity or
spectrum.
Various embodiments of the invention comprise an optical system and
method using a scanning configuration for scanning an optical scan
head relative to a sample substrate based at least relative linear
motion, a relative linear motion and a relative angular motion, two
relative angular motions, or any combination thereof.
Various embodiments of the invention comprise an optical system and
method having a low mass scan head for scanning a sample substrate.
A low mass scan head can, for example, contain a limited number of
components such that its inertial mass can be reduced and its
potential acceleration and velocity increased.
V. BRIEF DESCRIPTION OF THE DRAWINGS
Various embodiments of the present teachings are exemplified in the
accompanying drawings. The teachings are not limited to the
embodiments depicted in the drawings, and include equivalent
structures and methods as set forth in the following description
and as would be known to those of ordinary skill in the art in view
of the present teachings. In the drawings:
FIG. 1 is a side view in partial cross-section of a system
including a heater providing temperature stabilization for an LED
array according to various embodiments;
FIG. 2 is a view in partial side cross-section of a system
including a thermoelectric device providing temperature
stabilization for an LED array according to various
embodiments;
FIG. 3a is a side view in partial side cross-section of a system
including a fan and cooling fins providing temperature
stabilization for an LED array according to various
embodiments;
FIG. 3b is a top plan view of a capillary sample holder according
to various embodiments;
FIG. 4 is a top view in partial cross-section of a system including
a fan and heating element providing temperature stabilization for
an LED according to various embodiments; and
FIG. 5 is a side view in a partial cross-section of a system
providing a strong thermal conductive path according to various
embodiments.
FIG. 6 is a side view in a partial cross-section of a first low
mass scan head system according to various embodiments.
FIG. 7 is a side view in a partial cross-section of a second low
mass scan head system according to various embodiments.
FIG. 8 is a side view in a partial cross-section of a third low
mass scan head system having a dispersive spectrometer according to
various embodiments.
FIG. 9 illustrates embodiments for scanning of 2-dimensional
surface using one linear actuator and one rotation actuator, in top
views (a, b) and side view cross section (c).
FIG. 10 illustrates embodiments for scanning of 2-dimensional
surface using two rotation actuators, in top views (a, b) and side
view cross section (c).
It is to be understood that both the foregoing general description
and the following detailed description are exemplary and
explanatory only and are intended to provide a further explanation
of the various embodiments of the present teachings. The various
prophetic examples (i.e., "Example 1," "Example 2", etc.) and
headings associated therewith, are provided to illustrate various
embodiments and aspects of the present disclosure. Such examples
are intended to be considered within the scope of the present
disclosure as a whole, and aspects of one example may be combined
with another, according to various embodiments.
VI. DESCRIPTION OF CERTAIN EMBODIMENTS OF THE INVENTION
Reference will now be made in detail to certain embodiments of the
invention, examples of which are illustrated in the accompanying
drawings. Wherever possible, the same reference numbers will be
used throughout the drawings to refer to the same or like
parts.
The section headings used herein are for organizational purposes
only, and are not to be construed as limiting the subject matter
described.
All documents cited in this application, including, but not limited
to patents, patent applications, articles, books, and treatises,
are expressly incorporated by reference in their entirety for any
purpose.
Indefinite articles "a" and "an" carry the meaning of "one or more"
in open-ended descriptions, such as those containing the
transitional phrase "comprising."
According to certain embodiments, the present invention provides
optical systems configured to provide optical scanning or
interrogation of a sample substrate. The system can be actively
thermally compensated, passively thermally compensated, or both.
Optical systems according to certain embodiments comprise at least
a sample substrate, an LED, an optical detector, a temperature
dependent unit, an optional temperature sensor, and an active or
passive temperature compensation system or both. According to these
embodiments, the LED is configured to provide excitation light to
the sample substrate. The optical detector is configured to receive
emission light from the sample substrate and generate detection
data. Systems according to the present invention may, in various
embodiments, comprise more than one of a recited element, such as,
for example, multiple LEDs, multiple optical detectors, multiple
filters, or multiple temperature sensors, except as specified to
the contrary.
According to various embodiments, a system can comprise one or more
LEDs, photodiodes, operational amplifiers, and LED-current control
circuits. Such components may have temperature dependent
properties, meaning that their properties (e.g., LED intensity) can
change with temperature variations. A temperature compensation
system can, for example, maintain some or all of these components
at a constant temperature to eliminate or reduce changes in the
temperature dependent property or properties. The constant
temperature can be, according to certain embodiments, elevated from
an ambient temperature. The constant temperature can be, according
to certain embodiments, lower than an ambient temperature.
Similarly, the constant temperature may be at or near ambient,
according to certain embodiments. For example, the system
components can be held at a constant temperature above an ambient
temperature using a resistive heating element as a heat source
under the control of the temperature compensation system. As an
additional example of temperature compensation, a temperature
compensation system can also adjust detection data to compensate
for the effects of temperature changes. As other examples, a
temperature compensation system can distribute thermal energy,
provide thermal insulation or buffering, or any combination
thereof.
According to certain embodiments, the temperature dependent unit
("TDU") will include the LED, the optical detector, or both, as
well as optionally other elements. The TDU may also consist or
consist essentially of the LED, the optical detector, or both.
Thus, according to certain embodiments, the TDU may be coextensive
with its components, such as an LED. That is, the TDU is not
necessarily an element distinct from other specified elements of
the system. Rather, it can be, according to certain embodiments, a
designation for other specified components whose temperature is to
be monitored, controlled, regulated, or otherwise compensated.
Additionally, however, the TDU may also comprise additional
functional elements, such as circuitry, support elements (e.g., a
housing or support substrate, thermal control elements, and
combinations thereof).
As used herein, a "sample substrate" refers to a substrate or
plate, such as a plate containing wells or microwells used for
chemical or biological assays or screenings, that contains or is
configured to contain one or more samples to be optically examined.
The samples may be contained, for example, on a surface, in a
volume (such as a microwell), or in a capillary. The sample
substrate may also include or be associated with a thermal cycler
block to provide thermal control over the sample, such as for
thermal cycling used in PCR application.
Sample substrates can include or contain, for example, regions for
performing chemical and/or biochemical assays or screenings, where
the assays or screenings include a mechanism for optically
transduced measurement. The sample substrate can also be referred
to as the illumination target, or just "target," as provided in
U.S. Pat. No. 6,744,502 by Hoff and Oldham, which is hereby
incorporated by reference in its entirety.
The mechanism for optical transduction of the assay property or
result may be fluorescent tags, as just one example. As another
example, the optically transduced measurement may be based on
optical absorption, reflection, other spectroscopic responses, or
any combination of spectroscopic measurements. It may also entail
temporally static measurements, time resolved measurements, or
both. As further examples, the measurement can entail a spectrally
resolved or frequency domain measurement, such as a Fourier
transform method. As a still further example, it may entail
non-linear measurements, such as Raman and multi-photon
processes.
"Optical detector" refers to devices that convert electro-magnetic
energy into an electrical signal, and include both single element
and multi-element or array optical detectors. Thus optical
detectors are devices capable of monitoring an electro-magnetic
(e.g., optical) signal and providing an electrical output signal or
data related to the monitored electro-magnetic (e.g., optical)
signal. Such devices include, for example, photodiodes, including
avalanche photodiodes, phototransistors, photoconductive detectors,
linear sensor arrays, CCD detectors, CMOS optical detectors
(including CMOS array detectors), photomultipliers, and
photomultiplier arrays. According to certain embodiments, an
optical detector, such as a photodiode or photomultiplier, may
contain additional signal conditioning or processing electronics.
For example, an optical detector may include at least one
pre-amplifier, electronic filter, or integrating circuit. Suitable
pre-preamplifiers include integrating, transimpedance, and current
gain (current mirror) pre-amplifiers.
The term "temperature dependent property" is used herein to refer
to the property of a device or device element that is affected by
temperature. The temperature of the device or element is, of
course, fundamentally a temperature dependent property of the
device or element. The temperature dependent property may be
monitored, according to certain embodiments, using an absolute
scale, such as degrees Celsius, or as a relative value compared to,
for example, a set point or baseline value.
For example, according to certain embodiments, a temperature
dependent property may be one or more of a temperature, a
temperature dependent optical property, a temperature dependent
electronic property, a temperature sensor signal or response, or
any combination thereof.
According to certain embodiments, the temperature dependent
property may be, for example, an electrical property, such as
resistance, that is affected by temperature directly or indirectly.
Thus, as one example, the device (e.g., a temperature dependent
unit) may comprise an LED and the resistance of the LED (if
temperature dependent) would be a temperature dependent property of
the LED and of the device comprising the LED. Other electronic
components, such as optical detectors, including photodiodes, and
amplifiers may also have temperature dependent electrical
properties that can be monitored. For example, resistive elements
in transimpedance amplifiers may have temperature dependent
electrical properties that can be monitored.
The temperature dependent property may also include properties that
are a derived or indirect function of a temperature dependent
property. Thus, for example, if electrical resistance is a
temperature dependent property, current or voltage, which would be
functions of the resistance, could also be temperature dependent
properties. Other temperature dependent properties may include, for
example, temperature dependent properties of an optical detector,
such as a photodiode. For example, the "dark current" or noise of a
detector may be temperature dependent. Temperature sensors may thus
include electronic circuits and signal measurement devices or
elements configured to monitor, for example, dark current or
noise.
In addition to the exemplary electrical properties, temperature
dependent properties may include optical properties of optically
active components, such as excitation sources and optical
detectors. For example, for a conventional LED the intensity and
spectrum of its optical output may both be temperature dependent
properties of the LED. For commercial LEDs, such temperature
dependence is usually well characterized. As another example, the
amplitude and range of sensitivity and response of the optical
detector may also be temperature dependent. Temperature sensors may
thus include optical detectors.
A "thermal control signal" is understood to mean a signal that is
used or can be used to provide thermal control to a device. For
example, it may be the output of a temperature sensor. Such a
thermal control signal may be unprocessed or processed, including
unamplified or amplified. For example, a signal may be processed in
a computer or designated circuit, and a resultant derived or
calculated signal can be used to provide thermal control. The
resultant derived or calculated signal would also be considered a
thermal control signal.
The thermal control signal may be used, for example, to adjust the
power to a thermal control device, such as a heater or cooler, as
discussed elsewhere herein. The thermal control signal may also be
used, for example, to scale or compensate data to normalize
variations due to temperature changes, as also discussed elsewhere
herein.
A "temperature compensation system" is used herein to refer to any
system that can compensate for temperature changes. It may include,
for example, "active" thermal compensators that can actively add or
remove thermal energy. It may also include "passive" thermal
compensators that insulate or buffer temperature changes.
For example, a temperature compensation system may include an
active thermal compensation system that actively adjusts the
properties of a device to counter balance or offset other thermal
changes. Thus, it may include, for example, a system designed to
maintain a constant output intensity of an LED by, for example,
adjusting the applied current or voltage to compensate for
intensity changes caused by temperature variations. As another
example, to counter balance or offset other thermal changes the LED
duty cycle may be adjusted to maintain as constant the optical
flux, integrated over a given time period. Thus, the LED output can
be actively maintained at a constant, or relatively constant, level
by compensating for changes in temperature with changes to the
operating current or other control parameters (e.g., duty cycle).
An active temperature compensation system may also include systems
that scale or adjust data values to normalize variations due to
temperature effects, as discussed further below in the context of
temperature compensated detection data.
Other temperature dependent properties and thermal control signals
may also be used for active thermal compensation systems.
Similarly, other scaling or normalizing techniques may be used, and
may depend on a known or empirically derived relationship between
the raw detection data and the temperature dependent property.
The term "regulate," as used in the context of "configured to
regulate," means that the system, device, or element so configured
has the functionality to regulate a given property or function.
Being "configured to regulate" a given property or function does
not require that the system, device, or element is necessarily
always actively regulating the property or function. Further, the
regulation can be direct or indirect. For example, the thermal
control signal configured to regulate an operating temperature may
be processed or converted prior to transmission to the regulating
system.
"Detection data" refers to data derived from or related to the
optically transduced assay measurement. Thus the detection data may
be the output signal from an optical detector configured to receive
emission light from a sample substrate. It may also include such
signals that are further processed, by, for example, A to D
conversion, amplitude scaling, offset adjustment, frequency
modulation or demodulation, or other signal processing
techniques.
"Temperature compensated detection data" refers to detection data
that has been processed or otherwise scaled to compensate for
changes in temperature of one or more elements of the optical
system. For example, if the temperature and LED intensity vary
during the course of a fluorescence-based measurement, the measured
fluorescent emission intensity (detection data) will be a function
not only of the sample properties (e.g., fluorescent probe
concentration), but also a function of the LED intensity. Hence,
the measured fluorescent intensity will be a function of
temperature, and this can lead to undesirable inaccuracies in the
data. However, if the LED intensity (or a property correlated
therewith) is monitored, the data can be scaled based on this
intensity.
For example, if the LED intensity decreases with increasing
temperature, causing a subsequent decrease in sample emission
intensity, the temperature compensated detection data may have its
amplitude scaled (in this case increased) to compensate for
decreases in the LED intensity. Similarly, increases in LED
intensity can be compensated for by scaling, to reduce, the
amplitude of the detected data. One exemplary scaling method would
be to take the ratio of the raw fluorescent intensity to the
thermally dependent LED intensity or a correlated property (e.g.,
fluorescent intensity/LED intensity), to normalize LED intensity
variations where the fluorescent intensity is linearly related to
the LED intensity. Another exemplary scaling method entails using a
temperature dependent signal gain system, where the temperature
dependence of the signal gain system has the same absolute value
but opposite sign as the temperature coefficient being compensated
(e.g., the LED output intensity temperature coefficient). The
resultant scaled or normalized data would be temperature
compensated detection data, which is discussed further below.
As another example, if the background signal or "dark current" of a
detector increases with increasing temperatures of the detector, a
temperature dependent offset may be subtracted from the detection
data to remove temperature effects. Functionally, the purpose of
temperature compensated detection data is to provide a data output
where the effects of temperature changes have been minimized or
eliminated, as much as possible.
Active Temperature Compensation Systems and Methods
As part of an active temperature compensation system, a temperature
sensor can be present and be configured to provide at least two
functions. First, the temperature sensor can be configured to
monitor at least one temperature dependent property of the TDU.
Second, the temperature sensor can be configured to generate a
thermal control signal related to the at least one temperature
dependent property.
According to certain embodiments, an active temperature
compensation system and method may include passive temperature
compensation components, such as those discussed elsewhere herein.
Such passive components can be used either passively (e.g., a
cooling fan that is always on) or actively (e.g., a cooling fan
that is actively controlled), depending on the embodiment.
The temperature sensor can be used to measure directly, indirectly,
or by calculation, the temperature of the system components. The
temperature sensor can be configured according to various
embodiments to measure an operating temperature for various
components of the system. The temperature sensor can provide
feedback to a temperature regulating system. The temperature
regulating system can monitor the amount of heating or cooling
provided by a heat source or a heat sink to maintain the system
components at a nominal temperature within an acceptable deviation
value range. The temperature sensor can be used to form thermally
compensated detection data. Multiple temperature sensors may also
be used to measure, for example, temperature gradients or
temperatures of different components or parts of components.
According to certain embodiments, the temperature sensor can be a
component of the TDU or in thermal contact with the TDU.
Additionally, according to other embodiments, the temperature
sensor need not be in thermal contact with the TDU. The temperature
sensor can alternately or additionally monitor the TDU temperature,
according to certain embodiments, by monitoring a temperature
dependent property of the TDU. For example, in embodiments where
the LED is part of the TDU, the temperature sensor can remotely
(i.e., non-contact) monitor a temperature dependent optical
property of the LED. As another example, an optical response of the
optical detector can be monitored, where such a response (e.g.,
gain) is temperature dependent and the optical detector is part of
the TDU.
For example, according to certain embodiments, a temperature sensor
can be configured to monitor at least one temperature dependent
optical property of the temperature dependent unit. For instance,
an LED can be a component of the TDU and a temperature sensor can
be configured to monitor at least one temperature dependent
property of the LED. The temperature dependent property of the LED
can be, for example, a temperature of the LED, a temperature
dependent optical property of the LED, such as an optical output
power (emission intensity) or wavelength, or a temperature
dependent electrical property, such as resistance. Thus, according
to certain embodiments, a temperature sensor may be an optical
detector configured to monitor the LED emission. According to
certain embodiments, a temperature sensor may also be in thermal
contact with the LED or LED array.
According to various embodiments, the TDU can include one or more
optical detectors, such as first and second optical detectors. The
one or more optical detectors can be based on or include, as one
example, one or more photodiodes. According to certain embodiments,
a temperature sensor can be configured to monitor at least one
temperature dependent property of at least one of the first and
second photodiodes. The photodiode temperature dependent property
can be, for example, a temperature, a temperature dependent optical
property, such as its optical sensitivity, or a temperature
dependent electrical property, such as its resistance or dark
current.
Example 1
For example, FIG. 1 is side partial cross-sectional view of a
system 100 configured for active temperature compensation,
according to various embodiments, including an LED array 110 that
includes a plurality of LEDs 111. According to certain embodiments,
a single LED may be used, in which element 110 would be a single
LED. When multiple LEDs 111 are present, they may be of a common
type (i.e., common spectral properties) or they may be different,
and may be operated, for example, simultaneously, sequentially, or
any combination thereof. The system can also include a focal lens
106. The focal lens 106 can focus excitation light emitted by the
LED array 110. The LED array 110 can be in physical and/or thermal
contact with a substrate 112. The LED array 110 can include one or
more rows or patterns of individual LEDs. The substrate 112, which
can be a printed circuit board (i.e., PCB), can include one or more
highly thermally conductive layers that can distribute heat across
the substrate. The highly thermally conductive layer may be a
copper ground plane layer of a PCB board, or may be an additional
layer comprising, for example, aluminum or steel. The highly
thermally conducting layer may be, as possible examples, a surface
layer in direct contact with the thermal elements (e.g., LED array
110) attached thereto or may be an interlayer of a multilayer
substrate. A heating device 116, for example, a resistive heating
element, can be provided in thermal contact with the LED array 110.
The heating device 116 can be included in, on, or in and on the
substrate 112. The system 100 can include a temperature sensor 118
in thermal contact the LED array 110. The temperature sensor can be
centrally located with respect to the LED array 110. The
temperature sensor 118 can be included on the substrate 112. A
temperature regulator or temperature regulating system 122 can be
provided that is capable of receiving a signal from the temperature
sensor 118. The temperature sensor 118 and temperature regulating
system 122 can be integrated and/or can be of a unitary
construction. The temperature regulating system 122 can control the
heating device 116. The temperature regulating system 122 can
control a fan 114. The temperature regulating system 122 can
control the fan 114 and the heating device 116. For example, the
temperature regulating system 122 can be used to control the
heating device 116 to reach or maintain a nominal operating
temperature while the fan 114 prevents the operating temperature
from getting too high. This optimization can be used, for example,
if the LED array 110 is not on continuously. For example, heating
device 116 can provide additional heat when some or all of the
plurality of LEDS 111 in LED array 110 are not on. The fan 114 can
direct an air current over one or more cooling fins 104. The
cooling fins 104 can be in thermal contact with the LED array 110,
with the substrate 112, or with both. The temperature regulating
system 122 can send signals to and/or receive signals from the
temperature sensor 118, the heating device 116, and/or the fan 114.
The temperature regulating system 122 can send and receive signals
using wires 120, or via wireless controllers integrated in or
associated with the various components. Excitation light can be
emitted from LED array 110 and directed to one or more reaction
region 108 on a sample substrate. The reaction region 108 can
include a sample 107. The reaction region can be, for example, a
well on a microtiter tray. One or more optical signals from the
sample 107 may be monitored with a detector without or without
additional optical components, such as detector 130 and lens 144.
Although the axis between detector 130 and reaction region 108 is
generally perpendicular to the axis between LED array 110 and
reaction region 108, other configurations, such as a co-axial
configuration, may also be used according to certain
embodiments.
Example 2
FIG. 2 is a side cross-sectional view of a system 200, according to
various embodiments, that includes an active temperature
stabilization device for an LED array 210, for example, by
including a plurality of LEDs 211. A focal lens 206 can be included
to focus excitation light emitted from each of the individual LEDs
211. The LED array 210 can be in physical and/or thermal contact
with a substrate 212. The system 200 can include a temperature
sensor 218 in thermal contact with the LED array 210, the substrate
212, or both. The temperature sensor 218 can be included in or on
the substrate 212. A temperature regulating system 222 can receive
a signal from the temperature sensor 218. The temperature
regulating system 222 can control a thermoelectric device 214, for
example, a Peltier device. The thermoelectric device 214 can be in
thermal contact with the LED array 210, with substrate 212, or with
both. The thermoelectric device 214 can transfer thermal energy
from an ambient environment to the LED array 210. The
thermoelectric device 214 can transfer thermal energy to an ambient
environment from the LED array 210. The thermoelectric device 214
can include a temperature sensor. A plurality of cooling fins 204
can be in thermal contact with the LED array 210 and/or with the
thermoelectric device 214. The temperature regulating system 222
can send signals to and/or receive signal from the temperature
sensor 218, and/or the thermoelectric device 214, for example,
through wires 220. Excitation light can be emitted from LED array
210 and can be directed to a plurality of reaction regions 208, for
example, held in a thermal cycling block 230. The thermoelectric
device 214 can be used to maintain a lower temperature than could
be otherwise achieved under operating conditions. This can permit
the LED array 210 to operate more efficiently, with a higher total
flux output. The thermoelectric device 214 can be used in a heating
mode, for example, to reach or maintain a temperature when the LED
array 210 is not on. The thermoelectric device 214 can be used in a
cooling mode when the duty cycle of the LED array 210 is high
enough to require cooling. According to certain embodiments, there
may be a one-to-one correspondence between the number of LEDs 211
and the number of reaction regions 208, as shown. According to
other embodiments, there may be a greater number of LEDs than
reaction regions, for example as shown in FIG. 1. According to
still other embodiments, there may be a fewer number of LEDs than
reaction regions. As just one example, there could be three LEDs,
each having respectively different optical properties, that are
configured to illuminate a single reaction region. As another
example, there could be three LEDs, each having respectively
different optical properties, that are configured to illuminate
multiple reaction region, such as six or more.
Although thermal compensation can be used to maintain as constant
the temperature dependent spectral output of an LED, controlled
temperature variations may be used control the temperature
dependent spectral output of an LED to perform, for example,
spectroscopic analyses. For instance, in the case of an LED having
a 4.0 nm/.degree. C. coefficient of spectral changes per degree
centigrade, a 1 degree temperature change will change the LED
output spectrum by 4.0 nm. Thus, by changing the temperature of the
LED, such as by ramping or stepped changes, an LED can be used to
provide multiple optically distinct ranges of excitation light and
can be thus used to make, for example, spectrally dependent
measurements, such as an absorption spectral analysis. Such
thermally controlled-spectral analysis can be used independently or
in conjunction with a thermally compensated system or method to
provide additional levels of spectral analysis and discrimination.
For example, the LED temperature can be stepped between two
different temperature to provide two optically distinct ranges of
excitation light, and collected emission can be correlated with the
temperature, and hence optically distinct range, to discriminate,
for example, between two overlapping optical tags. As another
example, the LED temperature could be oscillated, and the emission
light can be analyzed based on this frequency, to discriminate
again background noise, for example. A phase analysis could also be
conducted on the emission light, to measure shifts from the phase
of the LED temperature oscillation, to provide a further level of
analysis for the emission light. The temperature of the LED may be
controlled with the same elements (e.g., heating and cooling
elements) discussed herein for use in temperature compensation, as
well as any other element functionally capable of applying or
removing heat.
Example 3
FIG. 3a is a side cross-sectional view of a system 300 according to
various embodiments and capable of providing temperature
stabilization for an LED array 310 including a plurality of
individual LEDs 311. A focal or collimating lens 306 can be
included to focus excitation light emitted from each of the
individual LEDs 311. The collimating lens can be a Fresnel lens. A
beam splitter 307, which can be a single element as shown or
multiple elements, can be included to separate excitation light
from emission beams. The beam splitter 307 can be replaced by a
filter or beam splitter as described, for example, in U.S. patent
application Ser. No. 10/735,339, filed Dec. 12, 2003, which is
incorporated herein in its entirety by reference. The LED array 310
can be in contact with a substrate 312. The system 300 can include
a temperature sensor 318 in thermal contact with the LED array 310.
The temperature sensor 318 can be included in, on, or in and on the
substrate 312. A temperature regulating system 322 can receive a
signal from the temperature sensor 318. The temperature regulating
system 322 can control a fan 314. The fan 314 can direct an air
current over a plurality of cooling fins 304. The cooling fins 304
can be in physical and/or thermal contact with the LED array 310.
The temperature regulating system 322 can communicate with the
temperature sensor 318, and/or the fan, through wires 320.
Excitation light can be emitted from LED array 310 and directed to
a reaction region 308 formed or disposed in, on, or in and on a
substrate 309. The reaction regions can include capillaries 330 of
a capillary array. The capillaries 330 can each have a portion that
passes through a detection zone 356.
FIG. 3b is a top plan partial view of the array of capillaries 330
shown in FIG. 3a, and the detection zone 356. The capillaries can
traverse the detection zone 356, where excitation light from the
LED array 310 (FIG. 3a) can be directed. For example, the
excitation light can be used for fluorescence detection of analytes
in capillaries of a capillary electrophoresis device. Such can be
the case in DNA sequencing and fragment length analysis
applications.
Active Temperature Regulation Systems and Methods
According to various embodiments, the active regulation of an
operating temperature of the TDU by the temperature compensation
system can be in any form capable of, in response to a control
signal, adding or withdrawing thermal energy from the TDU to
maintain a desired temperature value or range. For example, the
temperature compensation system can include elements such as
heaters, coolers, or fans, that are in thermal contact with the TDU
and that are activated or controlled (directly or indirectly) by
the thermal control signal. The temperature control system can
include a heater. The system can include a cooler. The system can
include both a heater and a cooler. Cooling and heating rates can
be augmented by using a plurality of heaters and/or coolers as
desired. If a heater is provided, it can comprise a plurality of
different types of heating devices. If a cooler is provided, it can
comprise a plurality of different types of cooling devices.
As one example, the temperature compensation system can comprise a
heating element and control electronics configured, with the
temperature sensor, to maintain the TDU at an elevated temperature
relative to the ambient temperature. Thus, assuming for this
example an ambient temperature of 20.degree. C., the temperature
compensation system can be configured to maintain the TDU at a
working temperature of 25.degree. C. to some specified degree of
precision. If the TDU temperature starts to drop below the set
point, as measured by the temperature sensor, the heater output
will be, via the thermal control signal, activated or increased to
raise (or stop the drop in) the TDU temperature. Similarly, if the
TDU temperature starts to rise above the set point, the heater
output will be, via the thermal control signal, deactivated or
reduced to lower (or stop the rise in) the TDU temperature.
An active temperature compensation system, according to various
embodiments, can be configured to regulate the operating
temperature of the TDU based on the at least one temperature
dependent property and optionally at least one non-temperature
dependent property.
The non-temperature dependent property may include, for example, at
least one property chosen from an age of the at least one optical
component, aging of electrical components, power supply variations,
changes in transmission or reflection of optical components such as
lenses and filters, altitude and air density effects such as lower
heat capacity of air used for heat transfer at higher elevations or
lower ambient pressures, an anticipated temperature change, a heat
capacity of the TDU, a temperature regulation lag time, and thermal
conductivities of materials in the system. Age in this context can
be either a real time age (i.e., months since constructed or first
operated) or an age in terms of amount of time in actual use.
Optical component age may be a relevant property since, for
example, LED emissive intensity may diminish with age independent
of temperature. To the extent age-related intensity losses and
other non-temperature dependent effects are not appropriately
accounted for, these effects may be improperly attributed, in
certain systems, to temperature effects, and therefore
inappropriately compensated.
An anticipated temperature change may be a relevant property
according to certain embodiments. For example, if a heat-generating
component (such as a thermal cycle used during PCR, which can
entail heating for denaturing, annealing, and extension steps) is
anticipated to be activated (or deactivated), it may be desirable
to begin to reduce (or increase) the TDU temperature in advance of
this event. Similarly, it may be desirable to provide less heat,
where added heat is necessary to maintain thermal stability, in
advance of the heat generating event.
Heat capacity (thermal mass) of the TDU can be relevant, according
to certain embodiments, to provide a scaling factor or magnitude to
the temperature regulation. Similarly, thermal resistance can be
relevant, according to certain embodiments, to provide a scaling
factor or magnitude to the temperature dependent regulation. Thus,
for example, for a relatively large TDU heat capacity and/or
thermal resistance, the magnitude of the active temperature
compensation may be relatively or proportionally large. Further,
heat capacity and thermal resistance can be used, according to
various embodiments, to adjust the temporal profile of the active
temperature compensation. For example, with the thermal equivalent
of a large electrical resistive-capacitive (RC) time constant, the
magnitude of the active temperature compensation may be relatively
or proportionally large at the beginning of a control cycle and
lower at later times.
Similarly, if there is a known, expected, or empirically determined
lag time for the effects of temperature compensation, this lag time
may be accounted for, according to certain embodiments, to avoid
over heating or cooling of the TDU. The lag time may be due, for
example, to the finite time required to provide or stop heating or
cooling from a heating or cooling element.
The regulation of the TDU operating temperature according to
certain embodiments, may comprise a feedback control based on at
least a difference between a measured value of the at least one
temperature dependent property and a desired value of the at least
one temperature dependent property. As an example, according to
certain embodiments, the temperature sensor may be configured to
monitor a rate of change in the at least one temperature dependent
property and generate the thermal control signal as a function of
the rate of change.
For example, if the desired temperature is 20.degree. C., to some
desired degree of precision, the degree or amount of temperature
regulation in response to a measured temperature of 30.degree. C.
could be greater in a proportional feedback system than that at a
measured value of 25.degree. C. As an example of one general
equation to express proportional temperature regulation, degree or
amount of temperature regulation ("regulative intensity" or "RI")
could be defined according to the equation
RI=X(T.sub.D-T.sub.m).sup.n, where X is a proportionality constant,
T.sub.D is a desired temperature, T.sub.m is a measured
temperature, and n is an exponent, such as 1, 2, or 3 (though it
could be any appropriate value, including non integers). As another
example, proportional integral differential (PID) feedback control
may be used. As still another example, a fuzzy logic feedback
system may be used. A feedback equation may further take into
various considerations, such as start-up or cool down times for the
temperature regulating element (e.g., heater), for example, as
discussed above.
According to various embodiments, the active temperature
compensation system can be configured to maintain the operating
temperature within an operating temperature range including a
minimum temperature and a maximum temperature separated by, for
example, about 15.degree. C., about 5.degree. C., about 1.degree.
C., or about 0.5.degree. C. The operating temperature range can
also be specified as a nominal temperature (e.g., 20.degree. C.)
and an acceptable deviation value or range (e.g., .+-.1.degree. C.
or .+-.0.5.degree. C.).
According to various embodiments, the active temperature
compensation system can include a user input device that is capable
of being programmed to maintain an operating temperature range
including a minimum temperature and a maximum temperature or a
desired temperature and temperature range. The system can include a
display capable of displaying the operating temperature of the
system.
According to various embodiments, the temperature compensation
system can include an error signaling device capable of signaling
an alarm when the operating conditions exceed a set point, such as
a temperature being greater than a maximum temperature, less than a
minimum temperature, or not responding at an expected rate.
According to various embodiments, the temperature sensor can
include a thermister, a thermocouple, a resistance temperature
detector (RTD), a non-contact temperature sensor, a bandgap
semiconductor resistive temperature detector, a platinum resistive
temperature detector, a bi-metallic temperature detector, a
combination thereof, or the like. Functionally, the temperature
sensor is configured to at least monitor the temperature dependent
property.
According to various embodiments, a system and method provide for
maintaining emission intensity and spectral stability of an LED.
The method can comprise: providing a system comprising an LED;
generating excitation light with the LED; measuring (directly or
indirectly) an operating temperature of the LED; and regulating the
operating temperature. The regulation may be by at least one of
transferring heat from the LED and transferring heat to the LED,
based on the operating temperature, to maintain, for example, the
temperature, emission intensity, and/or spectral stability of the
LED. The regulating can comprise retrieving from a memory source
adjustment data corresponding to a desired operating temperature or
temperature range at which emission intensity and spectral
stability of the LED are to be maintained.
Illumination Systems and Methods
An LED illumination system can provide consistent illumination, can
be light in weight, and can require minimal cooling and/or heating.
Where factors such as these are not important considerations, or
where there are other countervailing considerations such as
spectral or intensity demands that cannot be fulfilled with LEDs,
other light sources may be used instead or in addition to an LED.
For example, in a system where the illumination source is not to be
scanned, such as those discussed elsewhere herein, weight may not
be an important consideration and a non-LED source could be used,
according to certain embodiments.
The term "LED" or "light emitting diode" is used herein to refer to
conventional light-emitting diodes, i.e., inorganic semiconductor
diodes that convert applied electrical energy to light. Such
conventional LEDs include, for example, aluminum gallium arsenide
(AlGaAs), which generally produce red and infrared light, gallium
aluminum phosphide, which generally produce green light, gallium
arsenide/phosphide (GaAsP), which generally produce red,
orange-red, orange, and yellow light, gallium nitride, which
generally produce green, pure green (or emerald green), and blue
light, gallium phosphide (GaP), which generally produce red, yellow
and green light, zinc selenide (ZnSe), which generally produce blue
light, indium gallium nitride (InGaN), which generally produce
bluish-green and blue light, indium gallium aluminum phosphide,
which generally produce orange-red, orange, yellow, and green
light, silicon carbide (SiC), which generally produce blue light,
diamond, which generally produce ultraviolet light, and silicon
(Si), which are under development. LEDs are not limited to
narrowband or monochromatic light LEDs; LEDs may also include broad
band, multiple band, and generally white light LEDs.
The term LED is also used herein to refer to Organic Light Emitting
Diode (OLED), that can be polymer-based or small-molecule-based
(organic or inorganic), edge emitting diodes (ELED), Thin Film
Electroluminescent Devices (TFELD), Quantum dot based inorganic
"organic LEDs," and phosphorescent OLED (PHOLED). As used herein,
the terms "excitation source," "irradiation source," and "light
source" are used interchangeably.
Thus, according to certain embodiments, the LED can be a standard
semiconductor device, an organic LED, or an inorganic LED. Examples
of organic LEDs are QDOT-based LEDs and a nanotube-based LEDs. The
LED can be a stack of LED's such as a stack of organic LEDs or a
stack of organic LED layers.
According to various embodiments, the LED radiation source can
contain one LED or an array of individual LEDs. For example, super
bright LEDs can be used and can be arranged in a light array.
According to various embodiments, separate LEDs or a packaged set
of LEDs can be used in an array. According to various embodiments,
each LED can be a high power LED that can emit greater than or
equal to about 1 mW of excitation energy. In various embodiments, a
high power LED can be used that can emit at least about 5 mW of
excitation energy. In various embodiments wherein the LED or array
of LEDs can emit, for example, at least about 50 mW of excitation
energy, a cooling device such as, but not limited to, a heat sink
or fan can be used with the LED. Individual or arrays of
high-powered LEDs can be used that draw, for example, more than
about 10 watts of energy, about 10 watts of energy or less, about
five watts of energy or less, or about 3 watts of energy or less.
Exemplary individual LED and LED array sources are available, for
example, from Stocker Yale (Salem, N.H.) under the trade name LED
AREALIGHTS, and from Lumileds Lighting, LLC (San Jose, Calif.)
under the trade name Luxeon Star. According to various embodiments,
LED light sources can use about 1 microwatt (.mu.W) of power or
more, for example, about 5 mW, about 25 mW, about 50 mW, about 1 W,
about 5 W, about 50 W, or about 100 W or more, each individually or
collectively when used in an array.
As another example, high power red, blue and green emitters in a
one-piece package are available from multiple sources as off the
shelf items, and other colors are possible in custom-made packages.
High power LEDs in the LED package minimize the number of
individual or physically separate emitters required to generate the
necessary light output. Since each color in multi-element package
can be turned on and off separately, using such multi-element
packages as a excitation light source can provide wavelength
selectivity without extensive filter of the excitation light. Light
shaping and homogenizing optics may be used, according to certain
embodiments, to match the output of a multi-element package to that
of broad band sources and/or to improve illumination
uniformity.
According to various embodiments, the light source can include a
combination of two, three, or more LEDs, laser diodes, and the
like, such as, having a first relatively short wavelength (e.g.,
UV-blue) LED and a second "redder" or longer wavelength LED. For
example, the light source can include an LED that can emit
radiation at about 475 nm, an LED that can emit radiation at about
539 nm, and an LED that can emit radiation at about 593 nm.
According to various embodiments, excitation light emitted from the
light source can diverge from the light source at an angle of
divergence. The angle of divergence can be, for example, from about
5.degree. to about 75.degree. or more. The angle of divergence can
be substantially wide, for example, greater than 45.degree., yet
can be efficiently focused by use of a lens, such as the focusing
lens 106 (FIG. 1), 206 (FIG. 2), and 306 (FIG. 3). The lens can be
a collimating lens, for example, a Fresnel lens.
According to various embodiments, organic LEDs (OLEDs), such as
quantum dot LEDs can be used. See, e.g., U.S. patent application
Ser. Nos. 10/440,920 to Boege (filed May 19, 2003) and 10/440,852
to King (filed May 19, 2003), both incorporated by reference
herein. Quantum dots may also be used as optical tags or markers in
sample assays.
A quantum dot based LED can emit light in an emission band that is
narrower than an emission band of a normal LED, for example, about
50% narrower or about 25% narrower. The emission band of the
quantum dots can be a function of the size distribution of the
quantum dots, and thus can theoretically be extremely narrow. For
example, the quantum dot based LED can be tuned to emit light in a
relatively tight emission bandpass, for example, an emission
bandpass including a full-width of half-max (FWHM) of about 10 nm
or less, about 20 nm or less, or about 50 nm or less. Quantum dots
having a range or mix of sizes, composition, or both, can also be
used, to provide, for example, generally white light or light of
multiple specific wavelengths or wavelength ranges
The quantum dot based LED can increase the efficiency of the
system. The efficiency of a quantum dot based LED can theoretically
be higher than that of conventional LEDs, potentially about 90% or
more, for example, approaching 100%, such as when sandwiched
directly between two conductive films with each film directly
touching each quantum dot as opposed to the present 20% efficiency
typical for standard LEDs. Quantum dot based LEDs can be made
utilizing a slurry of quantum dots, where current flows through an
average of several quantum dots before being emitted as a photon.
This conduction through several quantum dots can cause resistive
losses in efficiency. Quantum dots can also provide many more
colors than conventional LEDs.
OLED films, including, for example, quantum dot based LEDs, can be
applied to a thermal block used for heating and cooling samples in
a fluorescence system without interfering with the operation of the
thermal block. According to various embodiments, an OLED can be
used and/or produced on a flexible substrate, on an optically clear
substrate, on a substrate of an unusual shape, or on a combination
thereof. Multiple OLEDs can be combined on a substrate, wherein the
multiple OLEDs can emit light at different wavelengths. Multiple
OLEDs on a single substrate or multiple adjacent substrates can
form an interlaced or a non-interlaced pattern of light of various
wavelengths. The pattern can correspond to, for example, a sample
reservoir arrangement or array. One or more OLEDs can form a shape
surrounding, for example, a sample reservoir, a series of sample
reservoirs, an array of a plurality of sample reservoirs, or a
sample flow path. The sample flow path can be, for example, a
channel, a capillary, or a micro-capillary. One or more OLEDs can
be formed to follow the sample flow path. One or more OLEDs can be
formed in the shape of a substrate or a portion of a substrate. For
example, the OLED can be curved, circular, oval, rectangular,
square, triangular, annular, or any other geometrically regular
shape. The OLED can be formed as an irregular geometric shape. The
OLED can illuminate one or more sample reservoirs, for example, an
OLED can illuminate one, two, three, four, or more sample
reservoirs simultaneously, or in sequence. The OLED can be
designed, for example, to illuminate all the wells of a
corresponding multi-well array.
According to various embodiments, an OLED can be used and can be
formed from one or more stable, organic materials. The OLED can be
capable of emitting light when a voltage is applied across the
organic material. OLDEs can use different electrically conductive
films or layers in electrical contact with the organic material to
provide the voltage path. At least one of the electrically
conductive films can be optically transparent, and may be chosen
from, for example, indium tin oxide (ITO), zinc oxide, and carbon
nanotube-based layers.
According to certain embodiments, an optical system may include two
or more LED scan be used, either simultaneously or sequentially.
The use of a plurality of different excitation wavelengths can
improve the use and accuracy of the calibration matrix used to
distinguish fluorescence emissions of various dyes.
For example, an optical system may include both first and second
LEDs configured to provide excitation light to the sample
substrate. The multiple LEDs may be similar or identical, to
provide, for example, increased intensity or uniformity as compared
with a single LED. The multiple LEDs may also be directed to
provide excitation light to different areas of the sample
substrate.
The multiple LEDs may also be different, for example being
configured to provide respectively different wavelength range
excitation light. The use of different wavelength ranges may be
used to, for example, probe different tags in a sample having (or
potentially having) different optical absorption properties. For
example, the first LED may have an emission spectrum suitable for
the absorption spectrum of a first fluorescent probe and the second
LED may have a different emission spectrum corresponding to or
suitable for the absorption spectrum of a second fluorescent probe
in the sample.
Multiple LEDs can be operated simultaneously, sequentially, or both
depending on the application. For example, multiple LEDs can be
operated simultaneously to provide enhanced intensity or
illumination of multiple areas on the sample substrate. Multiple
LEDs can also be operated simultaneously to provide multiple
excitation wavelengths, for example, to simultaneously provide
excitation light for multiple target probes.
According to certain embodiments, sequential operating of multiple
LEDs may be used, for example, to probe multiple target probes
and/or sample areas. Sequential operation can thus be used to
detect and distinguish among multiple optical signatures with as
few as one optical detector. For instance, according to certain
embodiments, the detection data from a single optical detector can
be synchronized to the sequential operation of the LEDs. For
instance, when LED #1 is activated the detection data from the
single optical detector will correspond to the probes and areas
that LED #1 is configured to illuminate, and when LED #2 is
activated (and LED #1 deactivated) the detection data from the same
single optical detector will correspond to the probes and areas LED
#2 is configured to illuminate.
The use of a plurality of different excitation wavelengths, such as
with multiple LEDs, can provide enhancements when used with a
calibration matrix used to calibrate an optical system prior to
measuring an unknown sample. In this regard, multiple LEDs may also
be used with or configured for use without performing an optical
calibration of the system. For example, a calibration may entail
directing the excitation light from multiple LEDs having multiple
distinct optical wavelength ranges onto the sample substrate and
measuring an optical response from the sample substrate, such as a
sample substrate having a calibration matrix of various dyes. A
calibration may further entail measuring the optical response from
the sample substrate with first and second optical detectors, and
calibrating the system based at least partially on the measured
optical response. The calibration may take into account, for
example, the absolute intensity of each measured optical response
as well as a ratio of different optical responses. Based on the
measured optical response, the calibration could include, for
example, a scaling factor for different excitation wavelengths to
account their respective intensities as determined using a sample
calibration matrix. The calibration could additionally or
alternatively include a scaling factor for different excitation and
or detection intensities or efficiencies for different areas on the
sample substrate. The calibration could additionally or
alternatively include a scaling factor to account for variations or
changes in the optical response of one or more of the optical
detectors. The scaling factor for the calibration may include, for
example, a constant term, a first order intensity correction,
and/or any higher order correction or scaling factors
Passive Thermal Control Systems and Methods
According to certain embodiments, there is a passive thermal
control system configured to passively control an operating
temperature of the TDU. The passive thermal control system may
comprise at least one of an insulating oven and a thermally
conductive substrate. A passive thermal control system and method
may also include active thermal control systems and methods as
discussed elsewhere herein.
An insulating oven as part of a passive thermal control system at
least partially encompasses the TDU, and is configured to provide
some degree of thermal insulation to the TDU. That is, an
insulating oven can be configured to provide thermal insulation
around a thermally sensitive device or element. In one embodiment,
an insulating area may be a thermally insulating box surrounding or
partially surrounding the thermally sensitive device or element.
The insulation may comprise, for example, polyisocyanate,
polyurethane, polystyrene, foamed polymers, gaps comprising air or
other low heat conducting gases, and vacuum gaps.
Insulation that can buffer against temperature changes may be used
according to certain embodiments. For example, insulation material
may comprise a material having a phase transition of, for example,
20.degree. C. Due to the additional energy required to change the
phase, e.g., from solid to liquid, the material will effectively
buffer against temperature changes at this phase change
temperature. In other words, if the material is in equilibrium
between two phases at 20.degree. C., additional heat added or
removed will not change the temperature of the material until the
material has fully transitioned to one of the two phases. These
materials are known as "phase change insulation" or insulation
containing a "phase change material." Polymeric materials, where
the phase change temperatures can be tuned by controlling
properties such as chain length and cross-linking, may be suitable
for this type of buffering. These buffering materials may also be
encapsulated, such as in microspheres, to further control their
thermal properties and enhance their handling.
Insulation based on phase change materials has been used in and
proposed for use in construction applications, such as in U.S. Pat.
Nos. 5,626,936 and 6,645,598 to Alderman, which are incorporated
herein by reference. Other phase thermal buffers based on phase
change materials are described in U.S. Pat. Nos. 5,290,904 to
Colvin, 6,703,127 to Davis, and 6,217,993 to Pause, which are also
incorporated herein by reference. According to certain embodiments
of the present invention, these materials and systems, and others
capable of providing insulation based on a phase change material,
may be used to provide thermal insulation. It is believed that the
phase change insulation has not been used as part of a temperature
compensated optical system, as disclosed herein.
Passive thermal compensation systems may also include thermal
conductive substrates designed to conduct thermal energy away from
a device in thermal contact therewith. For example, a thermally
conductive substrate as part of a passive thermal control system is
in thermal contract with the TDU and is configured to conduct
thermal energy between the temperature dependent unit and the
thermally conductive substrate.
A thermally conductive substrate may also provide a more uniform
thermal environment to multiple devices or elements in thermal
contact therewith. Depending on the thermal mass (i.e., total heat
capacity) of the thermally conductive substrate and elements in
thermal contact therewith, a thermally conductive substrate may
also act as a thermal buffer for the contacted devices or elements.
In such a case, a large thermal mass will minimize changes in
temperature with the addition or removal of thermal energy and
minimize variations in the temperatures of devices in thermal
contact therewith. A thermally conductive substrate may include or
be associated with cooling elements, such as cooling fins, to
dissipate heat and maintain a more stable thermal environment for
the contacted devices and elements.
A passive thermal control system may, according to certain
embodiments, comprise an insulating oven and a thermally conductive
substrate, as well as optionally other components. It may also
comprise, for example, additional components such as heaters,
coolers, or fans that are not activated by a thermal control
signal. For example, the passive thermal control system may
comprise a heat sink with cooling fins in thermal contact with the
TDU and a cooling fan directed at the cooling fins of the heat
sink, where the cooling fan is active during operation of the
system regardless of the TDU temperature. Additionally, as noted
elsewhere herein, a passive system may be combined with an active
system, such as a fan that is activated or deactivated based on
temperature changes.
As still further examples, a cooling system can comprise a heat
sink assembly, comprising, for example, a substantially planar base
in thermal contact with the TDU and fins extending from the base.
According to various aspects, the cooling system can include a fan
and/or at least one cooling member configured to control the heat
sink temperature. The fan and/or the cooling member can be actively
controlled, for example, or can be maintained in a steady state
(e.g., on). According to some aspects, the fan and/or the cooling
member can be operated to actively hold the heat sink at or near a
desired temperature.
According to certain aspects, an additional cooling member can be
configured to lower the temperature of the ambient air being
directed toward the heat sink by the fan. The cooling member can
lower the ambient air temperature by outputting a cooling fluid
such as, for example, CO.sub.2 (bottled or dry), liquid nitrogen,
pressurized air, or the like into the airflow path of the fan.
As further examples, the cooling member can comprise one or more
Cold Gun Aircoolant Systems.TM., such as those marketed by
EXAIR.RTM.. The Cold Gun uses a vortex tube, such as those marketed
by EXAIR.RTM., to convert a supply of compressed air into two low
pressure streams--one hot and one cold. The cold air stream can be
muffled and discharged through, for example, a flexible hose, which
can direct the cold air stream to a point of use, for example, in
the path of airflow from the fan to a heated surface such as, for
example, the heat sink. Meanwhile, the hot air stream can be
muffled and discharged via a hot air exhaust.
The cooling member can also comprise, for example, one or more
microchannel cooling loops, such as those marketed by Cooligy
(Mountain View, Calif.) for use with high-heat semiconductors. An
exemplary cooling loop can comprise a heat collector defined by
fine channels, for example, 20 to 100 microns wide each, etched
into a small piece of silicon, for example. In some embodiments,
the channels can be configured to carry fluid that absorbs heat
generated by a heated surface such as, for example, the heat sink.
In some embodiments, the cooling loops can be configured to absorb
heat from the ambient air in the path of airflow from the fan. The
fluid passes a radiator, which transfers heat from the fluid to the
air, thus cooling the fluid. The cooled fluid then return to a
pump, for example, an electrokinetic pump, where it is pumped in a
sealed loop back to the heat collector.
According to various aspects, the cooling member can comprise one
or more Cool Chips.TM., such as those marketed by Cool Chips plc.
Cool Chips.TM. use electrons to carry heat from one side of a
vacuum diode to another. As such, Cool Chips.TM. are an active
cooling technology, which can incorporate passive cooling
components, such as the fan. A Cool Chip.TM. layer can be disposed
between a heating system and the heat sink to introduce a gap
between the heating system and the heat sink. By addition of a
voltage bias, electrons can be encouraged to move in a desired
direction, for example, from the heating system to the heat sink,
while their return to the heating system is deterred by the gap.
Thus, the heat sink can be hotter without damaging the heating
system. In some aspects, one or more Cool Chips.TM. can be arranged
to absorb heat from ambient air to thereby cool the system.
According to certain embodiments, a passive control system can
comprise the thermally conductive substrate, the LED, and the
optical detector. According to these embodiments, at least the LED
and optical detector are components of the TDU and are in thermal
contact with the thermally conductive substrate. The thermally
conductive substrate is configured to conduct thermal energy
between (i) both LED and the optical detector and (ii) the
thermally conductive substrate.
An advantage of embodiments where the LED and the optical detector
are in thermal contact with a common thermally conductive substrate
is the enlarged thermal mass of the system. This enlarged thermal
mass may provide an enhanced degree of thermal stability or
compensation to the elements in thermal contact therewith. In
embodiments having both active and passive thermal compensation,
the active thermal compensation may be in thermal contact with the
thermally conductive substrate to provide active temperature
control to all elements in thermal contact with the thermally
conductive substrate, such as the LED and optical detector.
According to various embodiments, a thermal interface material
(TIM) can provide a good thermal contact between two surfaces, for
example, between an LED support and a substrate, and/or between an
LED housing and a thermoelectric device. The TIM can include
silicone-based greases, elastomeric pads, thermally conductive
tapes, thermally conductive adhesives, or a combination thereof.
Zinc-oxide silicone can be used as a TIM.
A thermal compliant pad TIM is described in U.S. Pat. No. 5,679,457
to Bergerson, which is incorporated herein in its entirety by
reference. Commercially available examples of thermal compliant
pads include those of Berquist Co. (Chanhassen, Minn.), including
their SIL-PAD.RTM. and GAP-PAD products, such as GAP PAD VO ULTRA
SOFT materials.
According to various embodiments, a TIM can be disposed between a
heat-transfer device and an LED. According to certain embodiments,
the TIM or thermally compliant pad may have a thermal conductivity
in the range of 0.08 to 5 w/m-K, or, as another example, depending
on the type, a TIM can have a thermal conductivity in the range of
0.08 to 0.37 W/m-K, 0.33 to 0.82 W/m-K, or 0.9 to 3 W/m-K, such as
available from Berquist Co (Chanhassen, Minn.).
For example, according to certain embodiments, a passive control
system includes a thermally conductive substrate that includes or
is in thermal contact with a thermally compliant pad. The thermally
compliant pad, which is also in thermal contact with the TDU, is
configured to conduct thermal energy between the TDU and the
thermally conductive substrate.
According to various embodiments, a heat conductive adhesive or
compliant pad can be used to attain good thermal conductivity
between a heat sink or heat source, and other system components,
for example, to maintain temperature stability in the system. A
heat exchange pathway can be established for system components such
as photodiodes and LEDs using a ground path to a common metal or
thermally conductive layer or plate as in, for example, a PCB
ground plane or other thermally conducting layer, such as a surface
or interior highly thermally conductive (e.g., aluminum or steel)
layer. The layer or plate can be a metal, for example, aluminum,
copper, or other electrically conductive metals. The system can
thus maintain temperature stability and keep various system
components at substantially the same temperature. The heat exchange
pathway can exchange heat with the ground plane or other thermally
conductive layer. Other thermal interface materials, for example,
adhesive backed resistive elements, can be used to achieve good
contact with the system components. For active thermal
compensation, a resistive heater can be disposed in or on a common
substrate (e.g., attached to the ground plane of a PCB) shared with
other electrical circuits included in the system, for example.
According to certain embodiments, thermal insulation can be used to
enclose or partially enclose the system components in a thermally
isolated environment. The enclosure can have openings allowing, for
example, illumination from the LEDs to illuminate a detection zone.
The insulation may also be optically transparent to allow light
transfer to and/or from the detection zone, and may be, for
example, glass or glass plates separated by a vacuum or fill with a
gas. Heat exchange pathways can be disposed in the enclosure to
allow for thermal transfer between the system and an ambient
environment. The heat exchange pathway can be, for example, a vent
in the enclosure. A cooling fan can cool the thermally isolated
environment provided by the enclosure. The heat exchange pathway
can include, as another example, a high conductivity thermal
surface included in the enclosure and in thermal contact with a
thermoelectric device. The system components can be separated from
the enclosure using a thermal insulator to lower a heat exchange
rate between the enclosure and the temperature control components.
According to certain embodiments, the thermally insulating
enclosure may contain components such as the excitation source, a
temperature sensor, and/or the temperature regulating system. Known
methods of heat transfer include conduction, convection, and
thermal radiation.
Example 4
FIG. 4 is a top plan cross-sectional view of a system 400. A
housing 401, also known as a cave, an oven, or an enclosure, can
include openings such as 403 and 407 as shown. LEDs 413, 415 can
irradiate through respective openings (403) to illuminate one or
more reaction regions (not shown). The opening 407 can allow
transmission or passing of emission beams from a reaction region to
a detector 440. One or more temperature sensor 418 can be disposed
in or on a housing substrate 412. The substrate 412 can include a
heating device 416. The temperature sensor 418 can be disposed on
or in the housing substrate 412. LEDs 413 and 415, and detector
440, can be disposed on or in the housing substrate 412. A
temperature regulator or temperature regulating system 422, capable
of receiving a signal from the temperature sensor 418, can be
included, for example, in the housing 412 or can be external to the
system. The temperature regulating system 422 can control the
heating device 416 and/or a cooling fan 414, as desired, for
example, to maintain the system 400 within a desired or pre-set
temperature range. The housing 401 can provide a relatively small,
thermally isolated, volume to be temperature-regulated by the
temperature regulating system 422. Control circuits (not shown)
necessary to utilize the LEDs 413, 415 and the detector 440 can be
housed within the housing 401. Excitation light can be emitted from
the LEDs 413, 415 and directed toward one or more reaction regions.
LED 413 can produce excitation light of a different wavelength
range than LED 415, for example, LED 413 can produce blue light and
LED 415 can produce green light. LED 413 can be operated
simultaneously or sequentially with LED 415.
Example 5
FIG. 5 is a side cross-sectional view of a system 500 according to
various embodiments. The system 500 can include photodiode
detectors 550, 552, and 554 disposed on a substrate 574. The
substrate 574 can have control circuits 560, 562, 564, and 566
disposed on a first surface or back side 575 thereof. The system
500 can include an LED 513 mounted on a plate 568 having a high
thermal conductivity. For example, the plate 568 can comprise
aluminum. An elastomer pad 570 having a high thermal conductivity
can be disposed between the substrate 574 and the plate 568. The
elastomer pad 570 can electrically isolate an electric resistive
heater 518 from the substrate 574. The photodiode detectors 550,
552, and 554 can be adhered or bonded or soldered to the substrate
574 using, for example, an adhesive 572. A temperature sensor 519
can be disposed in thermal contact with the system 500, for
example, the temperature sensor 519 can be disposed in contact with
the plate 568. Thermal insulation 576 can be disposed adjacent the
second surface or backside 575 of the substrate 574 to thermally
isolate the system 500 from an ambient environment. The system can
maintain the control circuits 560, 562, 564, 566, the photodiode
detectors 550, 552, 554, and the LEDs 511, 513, at the same
temperature. Accordingly, a constant and uniform temperature can be
maintained across the system 500.
Optical Configurations, Regulation Systems and Methods
Various embodiments of configurations of LEDs, reaction regions,
and intervening devices that can be used to direct excitation light
from light sources toward reaction regions, can be found, for
example, in co-pending U.S. patent application Ser. No. 10/440,920
entitled "Optical Instrument Including Excitation Source" to Boege
et al., co-pending U.S. patent application Ser. No. 10/440,852
entitled "Apparatus And Method For Differentiating Multiple
Fluorescence Signals By Excitation Wavelength" to King et al., both
filed on May 19, 2003, and U.S. patent application Ser. No.
10/735,339, filed Dec. 12, 2003, Reexamination Control No.
90/007,275, filed, Oct. 29, 2004, for U.S. Pat. No. 6,211,989, all
of which are incorporated herein in their entireties by
reference.
The LED or the LED array can include a plurality of LEDs mounted on
a substrate. The LED can be in thermal contact with a temperature
regulating system. The temperature regulating system can control a
heat-transfer device and/or a temperature sensor. The temperature
regulating system can maintain the operating temperature of the LED
such that the operating temperature does not change appreciably.
For example, the operating temperature can be maintained such that
it does not fluctuate by more than 10 degrees Celsius during
operation, for example, by not more than 5 degrees Celsius, by not
more than 1 degree Celsius, by not more than 0.5 degrees Celsius,
or by not more than 0.1 degree Celsius or less. The temperature
regulating system can maintain the operating temperature of the LED
such that the operating temperature does not exceed the bounds of a
programmed temperature range. According to various embodiments, a
temperature regulating system and a temperature sensor can be
included in a single-unit or can be included in an integrated
device, for example, a MAXIM DS1620 device available from Maxim
Integrated Products, Inc. of Sunnyvale, Calif.
The temperature sensor and the LED do not necessarily have to be in
physical contact. The temperature regulating system can adjust a
monitored temperature of the LED to compensate for any thermal
masses intervening between the LED and the temperature sensor and
to thus derive, calculate, or estimate an operating
temperature.
According to various embodiments, the LED can be cooled to maintain
life and illumination uniformity requirements of a system.
According to various embodiments, the LED can be cooled subambient
to achieve higher brightness. According to various embodiments, a
forced air cooling system or a thermoelectric device, for example,
a Peltier device, can be used to cool the LED and to keep the LED
from exceeding a maximum operating temperature. Additional cooling
members, as discussed above, may also be used, according to various
embodiments.
According to various embodiments, the temperature of the LED can be
monitored optically, for example, with an optical sensor, and
thermal characteristics of a system and spectral characteristics of
any LEDs embedded within the system, can be recorded. With an
understanding of the spectral coefficients of the LED as a function
of an operating temperature, the effects of a spectral shift can be
mitigated upon detection of optical properties of a sample.
According to various embodiments, system calibrations based on a
dye matrix or detection data can be altered in accordance with the
conditions (e.g., temperature) under which the dye matrix or
detection data was gathered or detected. Based on such calibrations
and compensations, thermal effects on excitation light emitted by
LEDs, including spectral shifts and intensity changes, can be
compensated, minimized, or eliminated, as much as possible.
According to various embodiments, the temperature of an LED can be
monitored and a computing apparatus can adjust the detection data
to compensate for the spectral shifts and/or intensity changes of
excitation light emitted from the LED. The compensation for the
shifting can be varied across wavelength ranges, for example,
different compensations can be provided for different wavelengths
of LEDs. A system can be provided that can include a data
adjustment unit comprising a memory adapted to store at least two
operating temperatures and at least one respective excitation beam
characteristic shift for each operating temperature. A plurality of
respective excitation beam characteristic shifts can be stored in
the memory. The adjustment data can be in the form of a plurality
of respective coefficients. Each coefficient can correspond to a
respective LED of an LED array. An exemplary range of coefficients
can be from about 0.04 nm/.degree. C. to about 4.0 nm/.degree. C.,
for example, based on deviation from a set or average operating
temperature. LEDs with higher and lower temperature coefficient may
also be used, consistent with various embodiments of the present
invention.
The coefficients can include two or more nominal temperature
coefficients corresponding to two or more LEDs. The coefficients
can be determined or designated based on the position of a
respective LED in an LED array. The spectral shift and temperature
coefficients can be different for different temperatures. The
spectral shift and temperature coefficients can be calculated,
determined empirically, or any combination thereof. During
operation, the spectral shift and temperature coefficients can then
be obtained, for example, from a look-up table. The table can be
sorted by temperature, for example. The table can be provided in a
long-term storage of a computer system, for example. Thermal
properties of multiple components (e.g., an LED and an optical
filter) can be combined to yield a combined thermal coefficient
that can then be used to compensate for system-wide (i.e., multiple
component) temperature effects. Multiple temperature sensors may
also be used to monitor the temperature of multiple components,
though multiple temperature sensors may also be used to monitor the
temperature of a single component
According to various embodiments, optical detection instruments
utilizing LEDs can obtain very stable intensity or spectral
characteristics by stabilizing an operating temperature of an LED.
Illumination stability can be important to minimize the signal
noise in the system. Illumination stability can improve the
sensitivity of the instrument to detect low concentration dyes.
Spectral stability can be used to maintain values for the
deconvolution matrix associated with a set of dyes to prevent
quantification errors. Similarly, variations in intensity resulting
from temperature changes can be different for different wavelengths
of LEDs, resulting in apparent spectral instability.
According to various embodiments, illumination stability can be
improved by allowing the illumination source to warm-up. According
to various embodiments, shutters can block excitation light from
reaching a sample to prevent bleach out (photo bleaching). For
example, according to various embodiments, shutters can block
excitation light from reaching a sample to prevent bleach out
during illumination source warm-up. The illumination source can be
brought to a desired operating temperature range prior to enabling
or turning on the illumination source, using a heater and/or a
cooler. Regulating the temperature of the illumination source prior
to enabling the illumination source can prevent the need for a
shutter and/or can reduce the warm-up time period. According to
various embodiments, samples can be subjected to a reaction or a
series of reactions, for example, temperature cycled in a nucleic
acid sequence amplification or in a sequencing process. According
to various embodiments, the shutter can be unblocked in
coordination with the reaction or the series of reactions, to
detect and collect data at an appropriate time, for example, during
a fluorescence detection reading of the sample.
According to various embodiments, laboratory instrumentation
utilizing a relatively more robust dye matrix can be less
susceptible to the spectral shift of an LED, such as
thermally-based spectral shifts, than a system with a relatively
less robust dye matrix. The AB 7500 system available from Applied
Biosystems of Foster City, Calif., can have a very good dye matrix
and can have little susceptibility to spectral shift for at least
most dyes.
According to various embodiments, an operating temperature of an
LED (as an exemplary temperature dependent component) can be
controlled with a Peltier-effect thermoelectric device, a heat
pump, an electrical resistance heating element (Joule heater),
fluid-flow through channels in a metal block, reservoirs of fluid
at different temperatures, tempered air impingement, a combination
thereof, or the like. According to various embodiments, the thermal
device can include a fan to direct air-flow over cooling fins, or a
cold bar to assist in a heat transfer between an LED and another
thermal mass, such as air. According to various embodiments, the
thermal conductivity of the LED and/or a platform supporting the
LED can be greater than that of a surrounding ambient environment,
for example, the surrounding air.
According to various embodiments, a thermoelectric device can be
used as a heat-transfer device, for example, an XLT module
available from Marlow Industries, Inc. of Dallas, Tex. Controls for
the thermoelectric device can include an adjustable-bipolar DC
output current power supply. The power supply can provide
programmable PID control/ramp to set point control, deviation
alarms, and automatic and manual operating modes. In reactions, for
example, real-time monitoring of Polymerase Chain Reaction (PCR)
reactions, thermoelectric devices can both heat and cool, as
desired, the LED by using a bi-directional or bi-polar power supply
under programmable and/or logic control. The programmable and logic
control can be provided by using a general purpose computer, or
custom built hardware, for example, a field programmable gate array
(FPGA) or micro controller. Thermoelectric devices can be
specifically designed to withstand the continuous temperature
excursions required in PCR use.
According to various embodiments, a heat-transfer device can
include a vapor-cycle device, for example, a Freon-based (or other
refrigerant) vapor compression or absorption refrigerator. In such
units, thermal energy can be extracted from a region, thereby
reducing its temperature, then rejected to a "heat sink" region of
higher temperature. Vapor-cycle devices can include moving
mechanical parts and can include a working fluid, while
thermoelectric elements can be totally solid state.
Example 6
According to certain embodiments, the present invention provides an
optical system comprising a sample substrate, an LED, first optical
detector and optionally one or more additional (e.g., a second)
optical detector(s), an excitation-emission selector, and an
emission selector. Such systems may, of course, include the active
and passive thermal control systems and components discussed
elsewhere herein.
For example, there can be at least one LED configured to provide
excitation light to a sample substrate, such as to a sample well.
The excitation light can be provided by way of an
excitation-emission selector (e.g., FIG. 8, element 616) or without
such a component, as in FIG. 1. As just one possibility, the
excitation-emission selector may be a interference element (e.g.
dichroic) configured to receive the excitation light at an
approximately 45 degree angle, relative to an axis normal to the
receiving surface of the dichroic. The interference element can be
configured to reflect, in this case also at a 45 degree angle,
excitation light towards the sample substrate. The
excitation-emission selector could also be a beam splitter, and
such a beam splitter could similarly be configured for
approximately 45 degree angles of incidence and reflection. Some
excitation light may pass through the excitation-emission selector,
and this stray light could be contained in a light trap as
discussed elsewhere herein. Additional elements, such as mirrors
and lenses, may be used between the LED and the excitation-emission
selector and/or between the excitation-emission selector and the
sample substrate to, for example, turn or shape the excitation
light along a desired light path.
The central wavelength of the excitation light can be, for example,
about 470 nm. First and second optical detectors can be configured
to receive emission light, by way of the excitation-emission
selector, from the sample substrate and generate detection data.
Additional optical detectors, such as a third optical detector, may
also be included according to certain embodiments.
As just one possibility, consistent with the illustrative example
above of configuring the excitation-emission selector at a 45
degree angle relative to the exciation light received from the LED,
the excitation-emission selector can be configured to receive
emission light from the sample substrate at an approximately 45
degree angle and transmit some or all of this emission light such
that it is directed towards the optical detectors.
Thus, the excitation-emission selector can be configured to provide
at least two functions: (1) direct the excitation light received
from the LED towards the sample substrate and (2) direct the
emission light received from the sample substrate towards the
optical detectors.
In the optical path from the excitation-emission selector towards
optical detectors, one or more emission selectors, can be
configured to receive the emission light from the
excitation-emission selector and to selectively direct (i) a first
optically distinct range of the emission light to the first optical
detector and (ii) a second optically distinct range of the emission
light to the second optical detector. According to certain
embodiments, additional emission selectors may be used to further
separate out sub-ranges of emission light and direct them to
respectively different optical detectors. Mirrors may also be used
according to certain embodiments to control the optical path of
light in the system, including the path of the emission light to
one or more optical detectors, such as by folding beams to obtain a
compact footprint.
For example, a first emission selector may be configured to
receive, at a 45 degree angle of incidence relative to its surface
normal, emission light from the excitation-emission selector and
reflect a first optically distinct range from the emission light
towards the first optical detector. The emission selector may be,
for example, an interference element configured to reflect, at a 45
degree angle, the first optically distinct range. Emission light
not reflected (or otherwise lost due to, for example, absorption)
by the first emission selector can pass through the first emission
selector towards the second optical detector. Having selectively
removed an first optically distinct range of light from the
emission light, the transmitted light will necessarily be a second
optically distinct range, which can be directed to a second optical
detector via, for example, a mirror. Additional optically selective
emission filters can be added to further separate the emission
light into more optically distinct ranges.
Other configurations would include the use of beam splitters to
separate out multiple portions of the emission light, each have the
same (or nearly the same) optical properties, with the possible
exception of intensity, which may be regulated by the type of beam
splitter (e.g., 50:50, 75:25) used. Thus, a first beam splitter
could be configured to receive emission light from the
excitation-emission selector, direct (via reflection, for example)
a fraction of the intensity towards a first optical detector and
direct (via transmission, for example) the remaining intensity
towards other optical detectors, such as a second optical detector.
A filter can then be used in front of each optical detector to
selectively direct or pass an optically distinct ranges of light to
each optical detector. Such filters can also be used in conjunction
with optical detectors even where a selective emission selector is
used to further prevent unwanted ranges of light from reaching the
detector.
In the case of either an optically selective emission selector or a
non-selective element used to direct emission light towards
detectors, other optical elements, such as lenses and mirrors, may
also be used. For example, one or more lenses can be used in the
optical path between the emission selector or beam splitter and the
optical detector to focus emission light towards an optical
detector. As another example, a mirror can be used to fold or
otherwise redirect the optical path.
As used herein, first and second "optically distinct ranges" of
light refers two ranges of light distinct from one another based on
at least one spectral property. For example, first and second
optically distinct ranges may have two different central
wavelengths, e.g., 520 and 555 nm, as in the case of fluorescent
emission from fluorophores FAM and VIC. As another example, first
and second optically distinct ranges may have two different ranges
between points of full-width at half-maximum (FWHM) amplitude, such
as a first range from 500 to 550 nm and a second range from 590 to
630 nm, to distinguish between fluorophores FAM and ROX. Optically
distinct ranges may, however, have some common features, such as
partially overlapping spectra. Thus, as one example, a first
optical spectral range from 515 to 565 nm would be considered
optically distinct from a second spectra range of from 555 to 595
nm.
An optical system may also include one or more lenses, such as
optional lenses discussed above in the optical path to the optical
detector(s). As another example, a system may include one or more
lenses configured to focus the excitation light towards the sample
substrate. As another example, a system may include one or more
lenses configured to substantially collimate the emission light and
direct the substantially collimated emission light to the
excitation-emission selector and/or the emission selector.
Collimation can be desirable, for instance, to provide better
wavelength selectivity for an interference filter.
As yet another example, a system may include one or more lenses
configured to both focus excitation light towards the sample
substrate and collect the emission light from the sample substrate.
For example, an objective lens (which may contain more than one
lens) may be used to both focus excitation towards a sample and
collect emission light from the sample. As a further example, the
lens may also collimate the emission light while directing it
towards the excitation-emission selector.
The excitation and emission light may pass through additional
components between the optical head and the sample substrate. For
example, a cover plate may be used to seal the wells of the sample
substrate. The cover plate may be heated to control or maintain a
temperature in the wells. Additionally, the sample substrate may be
or include a thermal cycler block to further control reaction
conditions, such as to control thermal cycling for PCR.
A system may, according to certain embodiments, also include
optical filters, such as on optical filter to prevent stray
excitation light from reaching the optical detectors. For instance,
such a filter may be located in the optical path between the
excitation-emission selector and the one or more optical detectors.
As one example, an optical filter can be a 513 nm long pass filter
to effectively block 470 nm excitation light but still pass longer
wavelength emission light. As also discussed above, an optical
filter may also be used in close proximity to an optical detector
to prevent unwanted light ranges from reaching that detector. For
example, the optical filter may be a narrow bandpass filter tuned
or set to a particular fluorescent emission wavelength range. An
optical filter may also be used to select or reject a particular
range of light from the LED.
One or more of the LED and optical detectors may be mounted on a
common support. The common support may be a thermally conductive
substrate and/or a PCB. The support may include control
electronics, such as for power and signal processing. Control and
processing electronics may also be located in a separate unit, such
as in a computer processor. A thermal interface material (TIM) to
provide heat conduction between the LED and optical detectors and
the support may also be used.
According to certain embodiments, the optical system may also
include a thermal compensation system with a TDU that includes at
least one of the LED and the first and second optical detectors.
The thermal compensation system may also comprise an active
temperature compensation system, a passive temperature control
system, or both.
According to certain embodiments, the excitation-emission selector
and the emission selector (collectively "optical selectors") may be
selective or non-selective. In the case of a selective
excitation-emission selector, it may be configured to selectively
direct the excitation light received from the LED towards the
sample substrate and selectively direct the emission light received
from the sample substrate towards the optical detector. Similarly,
a selective emission selector may be configured to selectively
direct a first optically distinct range of emission light to a
first optical detector and a second optically distinct range of
emission light to a second optical detector. "Selective" and
"selectively" as used herein with respect to optical elements used
to selectively direct or separate different optical wavelengths or
wavelength ranges does not necessarily entail 100% selectivity but
only requires a preferential discrimination between different
optical wavelengths, wavelength ranges, or other optical properties
(e.g., polarization). An Example of a non-selective
excitation-emission selectors or emission selectors would be a beam
splitter (e.g., a 50:50 beam splitter). A beam splitter used as an
excitation-emission selector could be configured to direct at least
a portion the excitation light received from the LED towards the
sample substrate and to direct at least a portion of the emission
light received from the sample substrate towards the optical
detectors. A beam splitter used as an emission selector could be
configured to direct a portion of received emission light to a
first optical detector and another portion having the same spectral
range to a second optical detector. Optical selectors may each
independently comprise at least one of an interference (e.g.,
dichroic), dispersive, beam splitting, filtering, and diffractive
optical elements. For example, diffractive optical selectors may be
chosen from, for instance, gratings (e.g., transmission and
reflection gratings) and holographic reflectors.
Functionally, optical selectors can be configured to, according to
certain embodiments, select a given wavelength or wavelength range
from a broader range or combination of wavelengths. For example,
the excitation-emission selector can be configured to selectively
reflect at, for instance, a 45.degree. angle of incidence,
excitation light in order to direct the excitation light from the
light source (LED) towards the sample. Optical selectors, such as
interference filters, may be used at other angles as well,
depending on the design and properties of the optical selector.
Similarly, other optical selectors, such as beam splitters and
absorptive filters, may be used at angles other than 45.degree.,
including both steeper and shallower angles of incidence. The
excitation-emission selector can also be configured to selectively
pass an emission light wavelength or wavelength range, in order to
selectively direct emission light from the sample toward an optical
detector. The emission selector, for example, can be configured to
pass a first wavelength range to a first optical detector and a
second wavelength range to a second optical detector.
According to certain embodiments the excitation-emission selector
may comprise at least one interference (e.g., dichroic) optical
element configured to selectively reflect one of the excitation
light and the emission light and selectively transmit the other of
the excitation light and the emission light. As another example,
the emission selector may comprise at least one interference (e.g.,
dichroic) optical element configured to selectively reflect the
first optically distinct emission range and selectively transmit
the second optically distinct emission range.
The optical selectors, such as an emission selector, may also
contain, according to certain embodiments, a dispersive element
such as a prism or grating. For example, a dispersive element may
be configured to disperse the received emission light, and to
selectively direct the first optically distinct portion of the
emission light to a first optical detector and direct a second
optically distinct portion of the emission light to the second
optical detector. According to certain embodiments, the first and
second optical detectors can be elements of a common multi-element
array detector, while according to other embodiments the first and
second optical detectors can be individual optical detectors, such
as two photodiodes.
According to certain embodiments, an optical selector may comprise
a tunable optical selection element, such as a rotating filter
wheel or other tunable filter, such as a birefringent tunable
filter. Exemplary filter wheels are disclosed in U.S. Pat. No.
5,784,152 to Heffelfinger, which is hereby incorporated by
reference in its entirety. ColorSelect.RTM. from ColorLink, Inc.
(Boulder, Colo.) is another example of a tunable filter, in
particular a birefringent tunable filter, suitable for use in
various embodiments.
According to certain embodiments, an optical system according to
the present invention may include a rotating emission filter wheel
comprising at least two optical filters, an index feature
associated with the optical filters, an index position sensor
configured to detect an angular position of the rotating emission
filter wheel, and a motor configured to rotate the rotating
emission filter wheel. For example, there may be at least three
optical filters. As another example, there may be five or more
optical filters. For example, according to certain embodiments, the
rotating emission filter wheel can be configured to selectively and
sequentially direct at least five different wavelength ranges of
emission light received from the sample substrate to the optical
detector. The optical filter wheel could be configured to operate
at different speeds, such as a position-to-position time (including
settling) of from 10 msec to 2 sec, such as from 10 msec to 0.1
sec.
According to certain embodiments, a rotating filter wheel can be
used as an emission selector to simultaneous process multiple
distinct emission wavelength ranges. Thus, for example, a first
optical filter can be configured to selectively direct (via
reflection, for example) a first selected wavelength range of
emission light received from the sample substrate to the first
optical detector and to selectively direct (via transmission, for
example) a second selected wavelength range of the emission light
received from the sample substrate to the second optical detector.
Additional optical filters on the filter wheel can similarly be
configured to simultaneously direct two distinct wavelength ranges,
one by, for example, reflection, and the other by, for example,
transmission.
According to certain embodiments, an optical system may also
include a selective optical component, such as a tunable filter or
monochromator, optically located between the LED and the sample
substrate configured to selectively direct a desired wavelength
range of the excitation light towards the sample substrate. Such a
selective optical component, functionally, selectively blocking or
passing respectively different wavelength ranges in order to stop
unwanted excitation light from being directed towards the detectors
such components are not limited to a traditional filters (e.g.,
long pass, band pass, short pass), but may include other optical
components capable providing the desired function. According to
certain embodiments it may include diffractive components and
polarization dependent components, by way of example.
A component is said to be "optically between" two other optical
components (e.g., first and second optical components) when the
light path between the first and second optical components passes
through or off of (e.g., reflect) the optical component in
question. Thus, an optical component need not be physically between
two other components to be "optically between" these
components.
According to certain embodiments an optical system may also include
a light trap configured to trap stray excitation light not directed
towards the sample substrate. The light trap can be located, for
example, to trap stray excitation light passing through an
excitation-emission selector. The light trap may include optically
absorbing materials, baffles, or both to prevent the light from
escaping out of the trap.
The light trap may also comprise additional elements, such as a
light detector configured to monitor at least one optical property
of the stray excitation light. For example, it could monitor total
intensity or intensity of a given wavelength or wavelength range,
such as when coupled with a filter (e.g., bandpass filter). Thus,
according to certain embodiments, an optical detector in a light
trap (or elsewhere in the beam path) may function as a temperature
sensor to monitor a temperature dependent optical property (e.g.,
intensity or spectrum) of the excitation source. An advantage of
this configuration is that the excitation light intensity can be
monitored without interfering with or detracting from the light
intended to illuminate the sample substrate.
Low Mass Scan Heads and Scanning Methods
An optical system according to certain embodiments includes a low
mass scan head. As used herein, a "low mass scan head" is
understood to mean a unit configured to scan relative to a sample
substrate, where the unit has a low inertial mass such that
scanning can occur at a relatively fast rate. According to certain
embodiments, a low mass scan head may entail a scan head having a
relatively low mass and/or configured for a relatively high
velocity and/or acceleration. "Low mass" scan heads are further
understood to refer to scan heads containing a reduced number of
components such that its mass is comparatively reduced. The
additional components may be included, for example, in an
associated fixed optical head.
For example, a conventional optical head, where both the light
source (LED) and the detector are scanned, has a mass of 2,200
grams and an acceleration of 3.2 m/sec.sup.2. In comparison, a low
mass system using the same components but where the optical
detector is in a fixed head, the light source (LED) is in a scanned
low mass scan head, and the fixed and scanned optical heads are
connected via an optical fiber, the low mass scan head mass is 800
grams and has an acceleration of 8.8 m/sec.sup.2. As a further
comparison, a low mass system using the same components but where
the optical detector and light source (LED) are both in the fixed
head and the scanned low mass optical head is connected via an
optical fiber to the fixed optical head, the low mass scan head
mass is 500 grams and has an acceleration of 14 m/sec.sup.2.
A low mass scan head may provide other benefits and features, such
as, for example, reduced instrument shaking during scanning based
on the lower mass being scanned, the shorter scan time enabled by
greater acceleration or velocity, or any combination thereof.
Further, low mass scan heads may be actuated with smaller motors
and drive trains, all of which contribute to a reduced overall
instrument footprint and potentially reduced cost as well.
According to certain embodiments, a low mass scan head may include
the proximal end of at least one optical fiber. The low mass scan
head can be configured to provide one or more functions, including
scanning relative to the sample substrate, directing excitation
light towards the sample substrate, collecting emission light from
the sample substrate, and directing the emission light to the
optical fiber proximal end. The optical fiber, having distal and
proximal ends, can be configured to conduct emission light from its
proximal to its distal end.
According to certain embodiments, an optical system may also
include a fixed optical head. The fixed optical head does not need
to be configured for scanning relative to the sample substrate.
Thus, it can be maintained in a fixed position and its mass does
not affect any relative scanning rate.
The fixed optical head can include, for example, the distal end of
the optical fiber and one or more optical detectors, such as the
first and second optical detectors. Functionally, according to such
embodiments, the fixed optical head can be configured to direct the
emission light from the distal end of the optical fiber and towards
the optical detectors.
Multiple scan heads may also be used. For example, there may be
multiple pairs of fixed and scanning optical heads. Each pair may
be configured, for example, to detect distinct optical signatures
by, for example, having different excitation sources or having
emission selectors configured to select different emission
wavelengths. Pairs of optical scanning heads may also be configured
optically the same or similar to each other, and be configured to
scan different locations on the sample substrate to, for example,
increase the overall scanning rate. There may also be multiple
scanning optical heads associated with a single fixed optical head,
and conversely there may be multiple fixed optical heads associated
with a singe scanning optical head.
Example 7
For low mass scan head configurations according to some
embodiments, an excitation source can be located in either a low
mass scan head or a fixed optical head, or both if multiple
excitation sources are used. For example, a low mass scan head can
include the LED. The low mass scan head can also include the
excitation-emission selector. An exemplary low mass scan head
system 600 where the low mass scan head includes both an LED 610
and an excitation-emission selector 616 is illustrated in FIG.
6.
The system includes a fixed optical head (not shown) and a scanning
optical head 660. The optical heads are optically connected via
optical fiber 650, which may be a single optical fiber or bundle of
optical fibers. Emission light is focused into the proximal end of
optical fiber 650 via lens 646. Emission light emerging from the
distal end of optical fiber 650 into the fixed optical head can be
collimated, for example via one or more lenses before being
directed to on or more detectors, as discussed elsewhere herein.
The LED 610 can be electronically controlled, for example, to a
stationary PCB board or control and reading device via electrical
connection 652. Electrical connection 652 can be used for other
functions as well, such as operating a thermal control system, if
present, or transmitting a signal from a temperature sensor, if
present. Optics for the selection and detection of the emission
light in fixed optical head can be configured as, for example,
discussed herein for the emission light subsequent to the
excitation-emission selector.
In operation, light emitted from LED 610 can be collimated by a
lens, pass though a filter 636 to narrow the emission wavelength on
route to excitation-emission selector 616. The excitation-emission
selector 616 can reflect at least some of the excitation light
toward the sample substrate 640, the excitation light being focused
by lens 642 and passing through cover plate 612. Emission light
from the sample substrate 640 can be collected with lens 642 and
directed to pass through the excitation-emission selector 616,
before being focused by lens 646 into the proximal end of the
optical fiber 650, on route to the fixed optical head.
Example 8
For low mass scan head configurations according to certain
embodiments, the fixed optical head may include the LED or other
excitation source. The fixed optical head containing the LED can be
configured to direct the excitation light into the distal end of an
optical fiber. According to these embodiments, the optical fiber
can be configured to direct the excitation light from its distal to
its proximal end, and the low mass scan head (which includes the
proximal end) can be configured to direct the excitation light from
the optical fiber proximal end towards the sample substrate.
As illustrated in FIG. 7, there can be a low mass scan head system
700 where the fixed optical head (not shown) includes at least one
LED and optical detectors, and other optional components (e.g.,
optical, electronic, and/or thermal components). According to
certain embodiments where the excitation source is in the fixed
head, alternate excitation sources, such as white light sources
(e.g., halogen lamps) and narrow band sources (e.g., lasers), may
be used instead of or in addition to LEDs. Excitation light from
the fixed optical head is focused, such as via one or more lens,
into the distal end of the optical fiber 650. The excitation light
exiting out of the proximal end of the fiber 650 is collected and
collimated with lens 646 and focused towards the sample with lens
642. Lens 642 also collects and collimates emission light from the
sample, and lens 646 then focuses the emission light into optical
fiber 650 for transmission back to the detector(s) in the fixed
optical head.
Example 9
According to certain embodiments, there is an optical system having
a detector assembly or fixed optical head that includes a
dispersive spectrometer configured to measure spectral properties
of the collected emission light. Such a dispersive spectrometer may
include, for example, a dispersive element configured to spatially
disperse the spectral components of the collected emission light. A
dispersive spectrometer may also include one or more detectors,
such as, for example, an array detector configured to concurrently
measure a range of the spectrally dispersed emission light. As
another example, a dispersive spectrometer may include a selection
element, such as a moveable slit or mirror, to sequentially direct
different spectral components of the dispersed emission light onto
detector.
One illustrative embodiment of a detector assembly dispersive
spectrometer is provided in FIG. 8. The illustrated embodiment
shows the exemplary dispersive spectrometer components 880, 882,
884 and the excitation source 610 in the fixed optical head, but
this is not required according to all embodiments of systems and
methods according to the present invention. For example, both the
dispersive spectrometer and the excitation source can be included
in a scanned optical head. As another example, a dispersive
spectrometer can be in a fixed optical head with the excitation
source in a scanning optical head.
As schematically shown in FIG. 8 for optical system 800, the
dispersive spectrometer includes dispersion element 880, such as a
transmission diffraction grating, which is configured to receive
emission light 890 and disperse it into multiple spectrally
distinct components 892, 894. Reflection gratings and refractive
elements, e.g. prisms, could also be used as dispersion elements
according to certain embodiments. Focusing lens 882 focuses the
spectrally dispersed emission light 892, 894 onto different
locations on a multi-element optical detector 884.
Scanning Configurations and Methods
According to various embodiments, scanning of optics relative to
the sample substrate can be performed in order to sequentially
interrogate multiple locations, such as multiple sample wells, on
the sample substrate. According to certain embodiments, scanning
may be accomplished with relative linear X and Y translations.
According to certain embodiments, scanning may entail relative
angular motions. According to certain embodiments, scanning may
entail a combination of relative angular and linear motions.
In this context, a relative motion is understood to mean that at
least one of the optics and sample substrate are moved such that
their position relative to each other changes. For example, a
relative motion between or scan of optics relative to a sample
surface may entail movement of the optics, with the sample
remaining in a spatially fixed position. It may also entail
movement of the sample, with the optics remaining in a spatially
fixed position. As another example, it may entail combined motions
of both the optics and the sample.
For example, according to certain embodiments, scanning may be
accomplished by a relative linear motion and a relative angular
motion about a rotational axis generally perpendicular to a surface
of the sample substrate. In this context, generally perpendicular
means that functionally, the scan head will remain sufficiently
equidistant from the plane of the surface such that refocusing of
the scan head optics is not necessary due to the rotational
movement. Thus, while according to certain embodiments rotational
axes may be aligned wholly perpendicular to a sample plane,
according to certain embodiments some deviation from perpendicular
is allowed so long that the scan head optics can still provide the
desired function.
According to certain embodiments, the rotary axis can be used to
align the optical system with the first row of sample. The linear
axis can be moved to scan over the first row of the sample. The
linear scanning can be, for example, at a constant speed. The
rotary axis will typically remain fixed during the linear scan, but
may be adjusted to optimize the optical alignment of the optics
relative to the sample. After the first row is completed, the
rotary axis aligns for the next row of samples and then holds its
position. As before, the linear axis can be scanned, and the
process repeated until the sample has been fully interrogated. As
one alternative, both linear and angular motions may be used
simultaneously to scan the surface.
A scan cycle can begin at a time, for example, T.sub.o, and can end
with a final time T.sub.f. The period of time for a cycle to
complete can vary depending on a number of factors including, but
not limited to, the number of wells in the set, for example 96; the
time required to position each well of the set under the detector;
the time required to detect and measure a signal from the
spectrally distinguishable species in each well; the time required
to move from one well to the next well; and the time for a reaction
in a well to occur. According to some aspects, the run time of a
reaction can be reduced by calibrating the temperature of each well
at the same time that the signal from the spectrally
distinguishable species is measured. This temperature calibration
can reduce the run time of the reaction while not affecting the
data integrity.
According to certain embodiments, the period of time between
measuring a signal from a first well to a second well can be less
than about 30 seconds, for example less than about 20 seconds, and
as a further example, less than about 5 seconds. Once a signal from
each well of the set has been measured then another cycle can
begin.
Over the course of the cycle, the temperature can increase and/or
decrease. For example, each well of a set of multiple wells can
have the same temperature, such as 60.degree. C., when the signal
from spectrally distinguishable species is measured in a first
cycle. After the signal from each well has been measured, the
temperature can be increased to, for example, a denaturing
temperature, and then decreased. However, for each subsequent
cycle, the signal from each well of the set can be read at the same
temperature as in the first cycle. For example, if all of the wells
during a first cycle are at about 60.degree. C., then all of the
well should be at about 60.degree. C. for each subsequent cycle
when the signals are read so that the data is not compromised.
In various aspects, including certain PCR applications, for
example, well #1 of the set can have a first temperature when its
signal is measured. The first temperature can be greater than or
equal to an annealing temperature of DNA. The temperature of the
thermal cycler block 1 can be slowly increased, and optionally held
for a period of time, so that well #2 of the set has a higher
temperature when its signal is measured as compared to well #1. In
another embodiment, the temperature can be slowly increased in a
linear relationship over time, for example, so that one temperature
is not held for a period of time. In some aspects, the temperature
can range from about 60.degree. C. to about 95.degree. C. over the
course of a cycle. For example, well #1 can have a temperature of
about 60.degree. C. and well #2 can have a temperature of about
61.degree. C. during a first cycle. For each subsequent cycle, the
temperature of the thermal cycler block can be calibrated so that
well #1 again has a temperature of about 60.degree. C. and well #2
can have a temperature of about 61.degree. C. The particular
temperature of each well is not important for the first cycle, so
long as during each subsequent cycle the temperature of each well
is substantially the same as it was during the first cycle.
Variations in scan speed can be compensated or accounted for in
various ways, such as according to U.S. Pat. No. 6,040,586 to Tor
Slettnes, incorporated herein by reference.
Example 10
As shown in FIG. 9, a 2-dimensional surface may be effectively
scanned by combining a rotation about a single rotational axis with
a linear axis scan. In FIG. 9a, the illustrated scanner has a
rotation arm 1020 with an axis L102. The rotation arm 1020 is
attached to the linear scanner 1010 via a rotational actuator 1022.
The linear scanner 1010 in configured to scan a single linear axis
L101. As shown, the rotational actuator 1022 rotates about the axis
perpendicular to the plane of the paper about the center of the
actuator 1022, such that it is generally perpendicular to the plane
of the sample. By combining rotational motions of rotational
actuator 1022 with linear motions along axis L101 of linear scanner
1010, any location, in particular any sample well 608, on the
sample substrate 640 may be interrogated with the optical system
1024. For the purpose of illustration, rotational arm 1020 is shown
in two different positions. Additionally, according to certain
configurations, there may be multiple rotational arms and
rotational actuators, each having at least one associated optical
system, with each arm configured to scan the substrate.
According to certain embodiments, the optical system 1024 can be,
for example, an LED-based scan head, with or without thermal
compensation, as discussed herein. Thus, for example, it may be a
low mass scan head, as also discussed herein.
As shown in FIGS. 9b, c, the linear actuator 1010 can be a composed
of, among other things, a stepper motor 1025 and a belt drive 1026.
The stepper motor actuator can be, for example, a NEMA 17 actuator.
The belt 1026 connects between the stepper motor 1025 and a
spring-based idler take-up arm 1030. When the actuator 1025 is
actuated, platform 1032, which is operably connected to belt drive
1026, is translated parallel to axis L101, while traveling on
bushings 1028, which can be bronze, plastic, or other functionally
suitable material. The rotational actuator 1022 is mounted on
platform 1032, and is also translated parallel to axis L101. The
rotational actuator 1022, which can also be, for example, a NEMA 17
actuator, rotates about its central axis, causing arm 1020 and
optical system 1024 to sweep out or be aligned to various wells 608
on substrate 640. As the rotational actuator 1022 is adjusted, the
longitudinal axis L102 of arm 1020 will be moved to different
angles relative to linear axis L101, though remaining in common
plane for 2-dimensional scanning of substrate 640.
Thus, for example, combined linear and rotational adjustments can
be used to position optical head 1024 about well 608a1. The linear
axis can then be scanned, such that the wells a1-a12 are scanned.
Combined linear and rotational adjustments can then be used to
position optical head 1024 above well 608b12, and then sample row b
can be scanned by scanning the linear axis.
Example 11
According to certain embodiments, scanning may be accomplished by
two relative angular motions about two respectively different
rotational axes generally perpendicular to the surface of the
sample substrate. The scanner includes two rotary axis scanners to
move the optics across a 2-dimensional surface. For example, a
first rotary axis (the "shoulder" rotation) is mounted to an
instrument base. A second rotary axis (the "elbow" rotation) is
mounted to an arm connected to the first rotary axis. According to
certain embodiments, one or both of the rotary axis scanners can be
direct drive actuators, and gear and pulley systems can thus be
avoided. Coordination of both rotary motions can achieve linear
scanning or point-to-point motions.
For example, as shown in FIG. 10, there is a first rotary
(shoulder) axis and shoulder actuator 1123 with actuator shaft 1124
having one end of an arm 1110 (shoulder arm) connected thereto. The
shoulder actuator 1123 is fixed to a base 1126, and is configured
to rotate its actuator shaft 1124 about its central axis A111 as
shown in FIG. 10c, and perpendicular to the plane of the page for
FIGS. 10a, b. The longitudinal axis L112 of the associated shoulder
arm 1110 is connected to the shoulder actuator rotational shaft
1124 such that it can be rotated parallel to the plane of the page
for FIGS. 10a,b. As shown in FIG. 10b, the longitudinal axis L112
of shoulder arm 1110 can scan or be set to various angles, such as
25.3.degree., 42.4.degree., and 61.3.degree. relative to reference
line L111.
Attached to the second end of the shoulder arm 1110 is a second
rotary (elbow) axis and elbow actuator 1128 with elbow actuator
shaft 1122, having one end of arm 1120 ("elbow arm") connected
thereto. The elbow actuator 1128 is connected to the second end of
the shoulder arm 1110 and is configured to rotate its shaft 1122
about its central axis A112 as shown in FIG. 10c, and perpendicular
to the plane of the page for FIGS. 10a,b. The longitudinal axis
L113 of the elbow arm 1120 is connected to the elbow actuator 1122
such that it can be rotated parallel to the plane of the page for
FIGS. 10a,b. As shown in FIG. 10b, the elbow arm 1120 longitudinal
axis L113 can scan or be set to various angles (e.g., 86.6.degree.,
92.2.degree., and 86.6.degree.) relative to the shoulder arm 1110
longitudinal axis L112. The rotational motions can be coordinated
to achieve rectilinear scanning, point-to-point scanning, or any
other scanning or motion across the 2-dimensional sample
substrate.
As shown in FIG. 10c, the scanning system can also include home
position switches or sensors, such as a home position sensor 1132
for the elbow actuator and elbow arm and a home position sensor
1134 for the shoulder actuator and shoulder arm. These, or other
tracking or monitoring devices, can be used to track the position
the scan head relative to the surface.
For example, prior to conducting a scan, the scan head can move to
or though the home position. The position of the scan head after
subsequent motions (such as scanning relative to the sample
substrate), such as by actuating a linear or rotation actuator, can
be referenced to the home position such that the position of the
scan head can be tracked. Thus, as a rotational actuator rotates
the scan head, the position may be tracked by the number of steps
specified by a stepper motor rotary actuator and the geometry of
the system. Of course, additional position sensors may be used as
well or instead, such as position sensors (e.g., rotary encoders)
integrated in an actuator. As another example, tracking the scan
head position relative to the sample substrate can be accomplished
based (in whole or in part) on a system calibration, which can be
calculated prior to the scan, that correlates scan time (or other
parameter) with scan position.
Based on the tracked (including subsequently calculated) position
of the scan head, detection data can be correlated to the various
regions on the surface, such as the various sample wells, in order
to correlate and assign the detection data to each sample well.
Calibration can also take into account other factors, such as a
phase lag of an actuator relative to a control signal.
Example 12
Although various scanning routines are possible, one exemplary
scanning routine would be rectilinear scanning. For instance, the
combination of a high duty cycle linear scanning combined with a
low duty cycle rotational adjustment could be used for efficient
rectilinear scanning. As another example, rectilinear scanning can
be accomplished with two generally perpendicular linear
scanners.
As an example of rectilinear scanning with a high duty cycle linear
scanning combined with a low duty cycle rotational adjustment, as
shown in FIG. 9, the scanner could be configured to begin at well
608a1 (i.e., column a, row 1) by a preliminary adjustment of the
rotational actuator 1022 and the linear actuator 1010. The scanner
could then be configured to linearly scan the wells parallel to
L101 to the end of the column, i.e., well 608a12, as depicted. The
linear scan could be maintained at a constant speed, for example.
The rotational arm 1020 could then be adjusted with rotational
actuator 1022 to align optical system 1024 with the center of the
wells in column b, and held to this angular position. Scanning
could then begin with well 608b12 to the first well in that column.
The scan could then continue in a similar manner up and down the
remaining columns of wells. At the beginning or end of each column,
the linear position of platform 1032 may need linear adjustment
parallel to L101 to optimize the alignment of the optical system
1024 with the first or last well in the column by accounting for
sine variations due to changes in theta.
Example 13
As another example, scanning could be effectuated in a
point-by-point manner. For example, the scan head could be aligned
over a first sample well and the sample well optically
interrogated. Then scan head would then be aligned over a second
sample well, with the cycle repeated until all desired sample wells
have been interrogated. Such point-by-point can be, according to
certain embodiments, accomplished with relatively fast moves of the
scan head from one position to the next together with relatively
slow movement, or even a specified dwell time with no movement,
over each well for interrogation. According to certain embodiments,
the point-by-point can entail generally continuous motion of the
scan head relative to the surface.
As an example of point-by-point scanning, coordination of both
rotary motions of the two axis rotary scanner can achieve linear
scanning or point-to-point motions. For example, as shown in FIG.
11b, an end of elbow arm 1120, which can contain detection optics
1024, is shown in three different positions over three different
samples wells 608, based on combinations of angles from the
shoulder 1124 and elbow 1122 rotary axes. As shown, when the first
rotary axis is at 25.3.degree. and the second rotary axis is at
86.6.degree., a first well can be interrogated. When the first
rotary axis is at 42.4.degree. and the second rotary axis is at
92.2.degree., a second well can be interrogated. Similarly, when
the first rotary axis is at 61.3.degree. and the second rotary axis
is at 86.6.degree., a third well can be interrogated.
Other embodiments will be apparent to those skilled in the art from
consideration of the present specification and practice of various
embodiments disclosed herein. It is intended that the present
specification and examples be considered as exemplary only.
* * * * *
References